Meaning: 'Exposure' means the condition of being in contact with something harmful or dangerous, such as air pollution in this context.

Wrong options:

• enclosure: 'Enclosure' refers to something being closed off or surrounded, which does not relate to the context of being subjected to pollution.
• foreclosure: 'Foreclosure' is a legal term related to property and debt, making it irrelevant in the context of health risks from pollution.
• composure: 'Composure' refers to a state of calmness or self-control, which does not fit the context of discussing health risks associated with pollution.

Correct answer: detail

Explanation: The word 'detail' is appropriate here as it indicates a thorough examination or analysis of the studies. It fits grammatically and contextually, as the researchers looked closely at the studies for their meta-analysis.

Meaning: 'Detail' means to describe or explain something thoroughly, which is what the researchers did with the studies.

Wrong options:

• favor: 'Favor' implies support or preference, which does not fit the context of analyzing studies.
• charge: 'Charge' typically refers to an accusation or a fee, neither of which relates to the examination of research studies.
• support: 'Support' suggests providing assistance or backing, which does not convey the act of closely examining the studies.

Correct answer: increased

Explanation: The word 'increased' fits grammatically as it describes a higher level of risk. Contextually, it aligns with the sentence's meaning, indicating that the risk of developing depression is heightened for those exposed to higher pollution levels.

Meaning: 'Increased' means made greater in size, amount, or degree, which accurately describes the heightened risk mentioned in the sentence.

Wrong options:

• decreased: 'Decreased' means made less, which contradicts the context of the sentence that discusses an increase in risk.
• last: 'Last' refers to duration or finality, which does not relate to the concept of risk in this context.
• less: 'Less' indicates a smaller amount, which is opposite to the intended meaning of heightened risk.

Correct answer: exceed

Explanation: The word 'exceed' is grammatically correct as it indicates going beyond a limit. Contextually, it fits perfectly as it refers to the WHO's guideline on air pollution levels that should not be surpassed.

Meaning: 'Exceed' means to go beyond a set limit or standard, which is relevant to the guideline mentioned in the sentence.

Wrong options:

• proceed: 'Proceed' means to continue or move forward, which does not fit the context of discussing limits on pollution levels.
• succeed: 'Succeed' refers to achieving a desired outcome, which is unrelated to the concept of limits in this context.
• impede: 'Impede' means to obstruct or hinder, which does not convey the idea of surpassing a limit.