Meaning: In this context, 'hitting' means to have a strong negative impact or effect on something, particularly referring to the economic consequences faced by poorer countries due to extreme heat.

Wrong options:

• defeated: Defeated is the past tense of defeat, which implies a completed action and does not fit the ongoing context of the sentence.
• hit: Hit is the base form of the verb and does not match the grammatical structure required here, which needs a participle to indicate the continuous impact.
• defeating: Defeating is the present participle form but implies an active action of overcoming, which does not fit the context of the sentence.

Correct answer: underestimated

Explanation: The word 'underestimated' is the past participle form of the verb 'underestimate,' which fits grammatically as it indicates that the costs have been evaluated as lower than they actually are. This aligns with the context of the sentence regarding the assessment of climate change costs.

Meaning: 'Underestimated' means to have judged something to be less than its actual value or significance, indicating that the true costs of climate change are higher than previously thought.

Wrong options:

• underutilized: Underutilized means not used to its full potential, which does not fit the context of evaluating costs; it implies a lack of use rather than a misjudgment of value.
• underpinned: Underpinned means supported or strengthened, which does not relate to the evaluation of costs and is therefore contextually incorrect.
• underexposed: Underexposed refers to something not being sufficiently exposed or revealed, which does not apply to the assessment of costs in this context.

Correct answer: contributing

Explanation: The word 'contributing' is the present participle form of the verb 'contribute,' which fits grammatically as it describes the ongoing action of the poorest nations in relation to climate change. It aligns with the context of the sentence, indicating that these nations are playing a role in climate change despite their minimal emissions.

Meaning: 'Contributing' means to give or add to something, in this case, referring to the role that poorer nations play in the broader context of climate change, even if it is minimal.

Wrong options:

• permeating: Permeating means spreading throughout, which does not fit the context of nations' roles in climate change; it implies a different kind of involvement.
• computing: Computing refers to calculating or processing information, which is unrelated to the context of nations' contributions to climate change.
• accommodating: Accommodating means providing space or making adjustments, which does not fit the context of discussing contributions to climate change.

Correct answer: spells

Explanation: The word 'spells' is the plural noun form that refers to short periods or instances of extreme heat. It fits grammatically and contextually, indicating that these brief occurrences have significant economic impacts.

Meaning: 'Spells' in this context means short periods of time characterized by a specific condition, here referring to instances of extreme heat that affect economic output.

Wrong options:

• effects: Effects are the results or outcomes of something, which does not fit the grammatical structure needed here as a noun describing periods of heat.
• lacks: Lacks is a verb meaning to be without, which does not fit the context of describing periods of extreme heat.
• qualities: Qualities refer to characteristics or attributes, which does not match the context of discussing specific instances of extreme heat.