Meaning: Diversity refers to the range of different species or types within a particular area, in this case, the variety of poison frogs.

Wrong options:

• exchange: Exchange refers to the act of giving and receiving, which does not relate to the variety of frogs.
• adjustment: Adjustment implies a change or modification, which does not fit the context of describing the variety of frogs.
• ideas: Ideas are concepts or thoughts, which do not pertain to the biological variety being discussed.

Correct answer: major

Explanation: The word 'major' is an adjective that indicates significance, fitting grammatically and contextually to describe the importance of the Andes as a source of diversity.

Meaning: Major means significant or important, indicating that the Andes play a crucial role in contributing to the diversity of the Amazon basin.

Wrong options:

• new: New implies something recent or fresh, which does not convey the importance of the Andes' contribution to diversity.
• experted: Experted is not a standard English word and does not fit grammatically or contextually.
• small: Small suggests insignificance, which contradicts the intended meaning of the Andes being a significant source of diversity.

Correct answer: reservoirs

Explanation: The term 'reservoirs' fits grammatically as a plural noun and contextually as it refers to large sources or stores of biological diversity, aligning with the overall theme of the sentence.

Meaning: Reservoirs refer to large supplies or sources, in this case, indicating areas rich in biological diversity.

Wrong options:

• basin: Basin refers to a geographical area but does not convey the idea of a source or store of diversity as effectively as reservoirs.
• sea: Sea refers to large bodies of saltwater, which is unrelated to the context of biological diversity in the Amazon.
• areas: Areas is too vague and does not specifically indicate a source of diversity.

Correct answer: counter

Explanation: The word 'counter' is a verb that means to oppose or contradict, fitting grammatically and contextually to indicate that the finding opposes a previous idea about Amazonian diversity.

Meaning: Counter means to act against or oppose, suggesting that the new findings challenge existing beliefs about biodiversity.

Wrong options:

• places: Places is a noun that does not convey the action of opposing or contradicting, making it unsuitable here.
• sets: Sets implies establishing or placing, which does not fit the context of contradicting an idea.
• areas: Areas is too general and does not convey the action of opposing a concept.

Correct answer: tropical

Explanation: The word 'tropical' is an adjective that describes the type of forest, fitting grammatically and contextually to specify the environment where Amazonian diversity is thought to have evolved.

Meaning: Tropical refers to regions near the equator characterized by warm temperatures and rich biodiversity, specifically relating to the Amazon rainforest.

Wrong options:

• trending: Trending refers to something currently popular or gaining attention, which does not fit the context of describing a type of forest.
• trading: Trading implies the exchange of goods or services, which is unrelated to the description of the forest type.
• tracing: Tracing suggests following or tracking, which does not describe the forest environment.

Correct answer: origin

Explanation: The term 'origin' is a noun that refers to the source or beginning of something, fitting grammatically and contextually to describe where the frogs have come from.

Meaning: Origin means the point at which something begins or arises, in this case, referring to the source of the poison frogs.

Wrong options:

• imagine: Imagine is a verb that means to form a mental image, which does not fit the context of discussing the source of frogs.
• accompany: Accompany is a verb meaning to go along with, which does not relate to the concept of a source or beginning.
• looking: Looking is a verb that does not fit grammatically or contextually as it does not describe a source.

Correct answer: basin

Explanation: The word 'basin' is a noun that refers to a geographical area, fitting grammatically and contextually to describe the Amazon basin as the focus of biodiversity.

Meaning: Basin refers to a low-lying area that collects water, in this context, it signifies the Amazon basin as a significant ecological region.

Wrong options:

• sea: Sea refers to large bodies of saltwater, which is not relevant to the context of biodiversity in the Amazon.
• river: River refers to flowing water bodies, which does not encompass the broader ecological context of the Amazon basin.
• area: Area is too vague and does not specifically indicate the geographical and ecological significance of the Amazon basin.