Meaning: 'Degrades' means to lower in quality or value, in this case, referring to the reduction of visibility due to haze.

Wrong options:

• simmers: 'Simmers' is a verb that means to cook slowly or to be in a state of suppressed activity, which does not relate to visibility.
• monitoring: 'Monitoring' is a gerund that does not fit as it does not describe an action haze performs on visibility.
• faced: 'Faced' is a past tense verb that implies confronting something, which does not apply to haze affecting visibility.
• organizing: 'Organizing' is a gerund that refers to arranging or structuring, which does not relate to the action of haze on visibility.
• announced: 'Announced' is a past tense verb that indicates a declaration, which does not fit the context of haze affecting visibility.
• encounters: 'Encounters' is a present tense verb that implies meeting or coming across, which does not describe the action haze has on visibility.

Correct answer: encounters

Explanation: The verb 'encounters' is appropriate as it is in the present tense and matches the subject 'sunlight.' It describes the interaction between sunlight and pollution particles, fitting the context of how haze is formed.

Meaning: 'Encounters' means to come across or meet, in this case, referring to sunlight meeting pollution particles in the air.

Wrong options:

• simmers: 'Simmers' does not fit as it refers to a cooking process and does not relate to sunlight interacting with particles.
• monitoring: 'Monitoring' is a gerund that does not describe an action sunlight takes; it refers to observing rather than interacting.
• faced: 'Faced' is a past tense verb that does not apply to sunlight's interaction with particles.
• organizing: 'Organizing' is a gerund that refers to arranging, which does not relate to sunlight's action in this context.
• announced: 'Announced' is a past tense verb that indicates a declaration, which does not fit the context of sunlight's interaction with particles.
• degrades: 'Degrades' is a verb that describes a negative effect but does not accurately describe the action of sunlight meeting particles.

Correct answer: monitoring

Explanation: The gerund 'monitoring' fits grammatically as it describes an ongoing action by the federal government. Contextually, it aligns with the government's efforts to track visibility in national parks, making it relevant to the topic of air quality.

Meaning: 'Monitoring' means observing or checking the progress or quality of something over a period of time.

Wrong options:

• simmers: 'Simmers' does not fit as it refers to a cooking process and is unrelated to the action of tracking visibility.
• degrades: 'Degrades' is a verb that describes a negative effect but does not fit the context of ongoing government action.
• faced: 'Faced' is a past tense verb that does not apply to the continuous action of monitoring visibility.
• organizing: 'Organizing' is a gerund that refers to arranging, which does not relate to the action of monitoring visibility.
• announced: 'Announced' is a past tense verb that indicates a declaration, which does not fit the context of ongoing monitoring.
• encounters: 'Encounters' describes an interaction, which does not relate to the action of monitoring visibility.

Correct answer: announced

Explanation: The verb 'announced' is in the past tense, which fits grammatically with the context of the government making a declaration in 1999. It logically conveys the action taken to improve air quality, aligning with the overall narrative.

Meaning: 'Announced' means to make a public declaration about something, in this case, the government's effort to improve air quality.

Wrong options:

• simmers: 'Simmers' does not fit as it refers to a cooking process and is unrelated to the action of making an announcement.
• monitoring: 'Monitoring' is a gerund that refers to observing, which does not fit the context of a past action of announcing.
• degrades: 'Degrades' describes a negative effect but does not fit as it does not relate to the action of announcing.
• organizing: 'Organizing' is a gerund that refers to arranging, which does not relate to the action of making an announcement.
• encounters: 'Encounters' describes an interaction, which does not fit the context of a government announcement.
• faced: 'Faced' is a past tense verb that implies confronting something, which does not apply to the action of announcing.