Biodiversity

Respuesta correcta: A) exacerbate

• A) exacerbateCorrect. 'Exacerbate' means to make a problem or bad situation worse, which fits perfectly here.
• B) alleviateIncorrect. 'Alleviate' means to make something less severe, which is the opposite of what's needed.
• C) mitigateIncorrect. 'Mitigate' means to make something less severe, which doesn't fit the negative consequence implied.
• D) facilitateIncorrect. 'Facilitate' means to make an action or process easy or easier, which is not appropriate for a social divide.

Respuesta correcta: D) Endemic

• A) MigratoryMigratory describes movement between locations, not natural restriction to one geographical area.
• B) DomesticatedDomesticated describes organisms changed through human breeding and management, not geographical restriction.
• C) InvasiveInvasive describes a non-native organism that spreads and causes harm, not a species naturally restricted to an area.
• D) EndemicEndemic describes a species whose natural distribution is restricted to a particular area.

Respuesta correcta: A) eradicate

• A) eradicate'Eradicate' means to destroy completely, and the sentence describes a chemical that eliminates an unintended population beyond the treated field.
• B) erect'Erect' means to set up or build, and the clause concerns the disappearance of insects rather than any physical construction.
• C) aspire'Aspire' means to have a strong ambition, and nothing in the sentence attributes any ambition to the pesticide or to anyone else.
• D) err'Err' means to make a mistake, and the sentence reports a biological consequence rather than any fault or error.

Respuesta correcta: A) reinvigorate

• A) reinvigorate'Reinvigorate' means to give fresh strength or energy to, and the sentence describes habitat returning to a condition that supports long-absent species.
• B) reinforce'Reinforce' means to strengthen or support, and the clause is about the return of species rather than added structural support.
• C) rejoin'Rejoin' would require a subject that had left and came back, but species were displaced locally rather than departing to be reunited.
• D) reject'Reject' means to refuse or refuse to accept, and the sentence describes a recovery rather than any act of refusal.

Respuesta correcta: C) To keep strips of native vegetation that connect patches of forest.

• A) To raise more goats in the canyon.Incorrect. Clearing land for goats is described as the main danger to the bird, so the foundation would not pay for more goats.
• B) To cut the low bushes and use them for firewood.Incorrect. The bushes are where the wren builds its nests, so cutting them would increase the threat instead of reducing it.
• C) To keep strips of native vegetation that connect patches of forest.Correct. The text says farmers are paid to leave native vegetation, and biologists compare these strips to bridges between forest patches.
• D) To catch the birds and move them to a zoo.Incorrect. Nothing in the text mentions capturing the wren; the strategy is to protect its habitat where it lives.

Respuesta correcta: D) Healthy mangroves help protect their source of income.

• A) They want to sell the wood to build houses.Incorrect. Cutting mangroves for construction is what caused the problem; the fishermen are planting them, not harvesting them.
• B) The national government ordered them to do it.Incorrect. The text calls Rafael a volunteer and mentions no order from any government.
• C) They need more space to build roads.Incorrect. Roads replaced mangroves in the past, so planting mangroves would take space away from roads, not create it.
• D) Healthy mangroves help protect their source of income.Correct. Mangroves shelter young fish, and Rafael says that without mangroves the fish, and their work, disappear.

Respuesta correcta: D) A forested corridor connecting two reserves

• A) Two forested reserves without a connecting corridorThis phrase denies the connection and makes reserves, rather than corridor, the main referent.
• B) A reserve connecting two forested corridorsThis phrase reverses the relationship: the original corridor connects reserves, not the other way around.
• C) A corridor connecting two unforested reservesThis phrase omits the corridor's forest cover and adds an unsupported claim about the reserves.
• D) A forested corridor connecting two reservesCorridor is the head noun, forested describes it, and connecting two reserves identifies its function.

Respuesta correcta: C) Easily damaged or harmed.

• A) Very large and difficult to cross.Incorrect. The text describes how pollution harms the wetlands, not their size or how hard they are to cross.
• B) Full of tourists all year.Incorrect. Tourists are never mentioned; 'fragile' describes how the ecosystem reacts to damage.
• C) Easily damaged or harmed.Correct. The sentence after 'fragile' shows that rubbish and chemicals quickly kill fish and drive animals away, so the wetlands are easily damaged.
• D) Dangerous for people to visit.Incorrect. The danger in the text is to the animals and the water, not to human visitors.

Respuesta correcta: C) Because stepping on slow-growing plants can damage them for many years.

• A) Because the trails lead to the best places for photos.Incorrect. Photography is never mentioned; the rangers' reason is the protection of the plants.
• B) Because visitors could get lost in the fog.Incorrect. Fog is mentioned as a source of water for the plants, not as a danger to visitors.
• C) Because stepping on slow-growing plants can damage them for many years.Correct. The last sentence says one footstep can damage a plant that took decades to grow, since frailejones grow about 1 cm a year.
• D) Because the frailejones are dangerous to touch.Incorrect. The text presents the plants as vulnerable, not as dangerous to people.

Respuesta correcta: B) is

• A) areAre incorrectly agrees with the plural noun sites inside the modifying phrase; the subject's head is singular protection.
• B) isIs agrees with the singular head noun protection; of nesting sites near the wetland modifies that noun.
• C) haveHave neither agrees with singular protection nor forms the required link between the subject and essential.
• D) wereWere uses plural agreement, whereas the head noun protection requires a singular verb in this statement.

Respuesta correcta: C) had

• A) hasIncorrect. The sentence refers to a past sequence, requiring the past perfect in inversion.
• B) wasIncorrect. 'Was' does not fit the past perfect structure required by 'Hardly'.
• C) hadCorrect. 'Hardly had...' is a classic C1 inversion structure used for sequential events.
• D) didIncorrect. 'Did' would require the base form of the verb, not the past participle 'been'.

Respuesta correcta: B) did

• A) had'Not until' inverts the main clause, placing the auxiliary before the subject 'the pollinator counts'. 'Had the pollinator counts begun' would leave the subject first, which the pattern forbids.
• B) did'Not until the ban took effect did the counts begin to recover'. The auxiliary is fronted to invert the clause, which is the defining feature of the structure.
• C) was'Was' would suggest a passive or a singular subject. The subject is plural but the verb is active, so a passive reading is not available.
• D) do'Do' is present tense and cannot invert a past sequence in which the ban had already come into force.

Respuesta correcta: B) does

• A) do'Do' agrees with plural subjects, and 'a restored marsh' is singular, so the base form with 'does' is required.
• B) does'Rarely does a restored marsh recover'. With a singular subject the inversion uses 'does', and the main verb reverts to the base form 'recover'.
• C) have'Have' would give the perfect aspect, but the bare inversion with 'rarely' and a singular subject takes 'does' before the base form.
• D) are'Are' cannot invert with a singular subject and would require a plural or a collection for agreement.

Respuesta correcta: A) did

• A) did'Only after the corridor was connected did the lynx range expand'. The auxiliary is fronted ahead of the subject while the main verb stays in the base form.
• B) had'Only after' frontes a subordinate clause and then inverts the main clause, so the auxiliary has to precede the subject 'the lynx range'.
• C) were'Were' would be needed for a passive main clause, but 'the lynx range expand' is active and the subject is singular.
• D) could'Could' is a modal and would not invert this past sequence; the tense auxiliary of the clause has to be the one that is fronted.

Respuesta correcta: A) The first phrase makes amphibians the object of the threat; the second makes the survey threatened.

• A) The first phrase makes amphibians the object of the threat; the second makes the survey threatened.The adjective attaches to amphibians in the first phrase and to survey in the second, changing what faces a threat.
• B) Both phrases say that the amphibians face a threat.In the second phrase, threatened modifies survey rather than amphibians, so the meanings differ.
• C) The first phrase describes a threatened survey, while the second describes threatened amphibians.This reverses the modifiers: threatened directly precedes amphibians in the first phrase and survey in the second.
• D) Moving the adjective changes only the number of amphibians surveyed.Neither phrase gives a number; moving threatened changes which noun the adjective describes.

Respuesta correcta: A) Recovery is the head; the modifiers specify what recovered and where.

• A) Recovery is the head; the modifiers specify what recovered and where.Recovery names the event, of native fish populations identifies what recovered, and in restored streams supplies the location.
• B) Researchers is the head; the modifiers explain who conducted the recovery.Researchers is part of the object after surprised, not the head of the subject.
• C) Streams is the head; the modifiers identify which researchers were surprised.Streams occurs inside a modifying phrase and does not identify the researchers.
• D) Populations is the head; the subject states that the researchers recovered.Populations belongs inside the phrase of native fish populations; the sentence reports fish-population recovery, not researcher recovery.

Respuesta correcta: B) The current strategy is directed towards the wrong objective.

• A) They are literally looking for something in the trees of Medellín.Incorrect. This reads the idiom literally; nobody in the debate is searching real trees, because the expression is figurative and describes a mistaken line of action.
• B) The current strategy is directed towards the wrong objective.Correct. 'Bark up the wrong tree' means aiming your effort at the wrong cause or target, so the speaker is saying the current plan on biodiversity points in the wrong direction.
• C) The approach is too noisy and aggressive.Incorrect. 'Barking' here does not describe a loud or aggressive tone; the idiom is about choosing the wrong objective, not about how people speak.
• D) A new environmental project involving trees should be started.Incorrect. The word 'tree' belongs to a fixed expression, so the speaker is not proposing a project with trees; the speaker is criticising the approach under discussion.

Respuesta correcta: A) Stop existing completely as a species.

• A) Stop existing completely as a species.Correct. 'Die out' means to disappear until no members of a species remain, and 'completely' reinforces that meaning.
• B) Leave the páramo and live in the city.Incorrect. 'Out' does not mean moving to another place here; the phrasal verb refers to extinction.
• C) Die only during the dry season.Incorrect. 'Die out' describes a permanent loss of a whole species, not deaths during one season.
• D) Become larger in number.Incorrect. This is the opposite meaning; the researcher says the species are 'disappearing'.

Respuesta correcta: B) Investigate and reduce the pollution, then assess whether releases are also needed.

• A) Increase releases while leaving water quality unexamined.More releases do not address the polluted habitat identified as a possible cause of continued decline.
• B) Investigate and reduce the pollution, then assess whether releases are also needed.This revision addresses the suspected underlying cause before deciding whether adding frogs would support recovery.
• C) Describe the released frogs as healthy without checking the stream.The frogs' initial health does not establish that the polluted stream can support their survival.
• D) Replace population monitoring with publicity about the releases.Publicity provides no evidence that the habitat problem has been resolved or that the population is recovering.

Respuesta correcta: D) The action is positive but very small compared with the size of the problem.

• A) The trees will be washed into the sea.Incorrect. This reads 'drop in the ocean' literally; the idiom describes size, not water carrying the trees away.
• B) Planting trees is a waste of time and should stop.Incorrect. The teacher calls it 'wonderful', so she values the action; she only says it is not enough.
• C) The river has too much water.Incorrect. The idiom does not refer to the amount of water in the river.
• D) The action is positive but very small compared with the size of the problem.Correct. 'A drop in the ocean' means a very small amount compared with what is needed, and 'we need bigger changes too' confirms this.