A.I. Explanation:

Correct answer: characteristics

Explanation: The word 'characteristics' fits grammatically as it is a plural noun that refers to the qualities or features of the atmosphere being modified by pollution. This aligns with the context of discussing how air pollution alters the natural state of the environment.

Meaning: Characteristics refer to the distinguishing traits or features of something, in this case, the atmosphere.

Wrong options:

• morbidity: Morbidity is a noun that refers to the condition of being diseased or the incidence of disease, which does not relate to the qualities of the atmosphere.
• pollution: Pollution is a noun that refers to the presence of harmful substances in the environment, but it does not describe the qualities of the atmosphere itself.
• selection: Selection is a noun that refers to the act of choosing or picking, which is unrelated to the context of environmental qualities.
• entitled: Entitled is an adjective that means having a right to something, which does not fit the context of describing atmospheric features.

Correct answer: morbidity

Explanation: The term 'morbidity' is appropriate here as it refers to the incidence of disease, which is directly related to the health impacts caused by air pollution. This fits both grammatically and contextually within the sentence discussing health outcomes.

Meaning: Morbidity refers to the state of being diseased or the prevalence of disease in a population.

Wrong options:

• characteristics: Characteristics refers to features or qualities, which does not relate to health outcomes or disease incidence.
• pollution: Pollution refers to the contamination of the environment, but it does not specifically address health impacts or disease rates.
• selection: Selection refers to the process of choosing, which is not relevant to the discussion of health impacts from air pollution.
• attributable: Attributable is an adjective that means capable of being assigned to a cause, which does not fit as it does not describe a health condition.

Correct answer: attributable

Explanation: The word 'attributable' is an adjective that indicates something can be assigned to a particular cause, in this case, the diseases caused by air pollution. It fits grammatically and contextually as it describes the burden of disease linked to pollution.

Meaning: Attributable means capable of being assigned or credited to a specific cause or source.

Wrong options:

• characteristics: Characteristics does not fit as it refers to features or qualities, not the causal relationship with disease burden.
• morbidity: Morbidity is a noun that refers to disease incidence, which does not describe the relationship of disease burden to pollution.
• pollution: Pollution is a noun that refers to environmental contamination, which does not convey the idea of causation in this context.
• selection: Selection refers to the act of choosing, which is unrelated to the causal relationship between disease and pollution.