Meaning: 'Migrate' means to move from one region or habitat to another, especially in response to seasonal changes, such as fish moving to cooler waters in summer and returning in winter.

Wrong options:

• immigrate: Immigrate refers to coming into a new country or region to live, which does not apply to the context of fish moving within their natural habitats.
• emigrate: Emigrate means to leave one's country to live in another, which is not suitable here as it implies a permanent move rather than seasonal movement.
• ingrate: Ingrate refers to an ungrateful person, which is unrelated to the context of fish behavior and does not fit grammatically.

Correct answer: adapt

Explanation: The word 'adapt' is appropriate as it indicates the ability of species to adjust to changing environmental conditions, fitting both grammatically and contextually in the sentence. It describes how populations respond to warmer waters, aligning with the overall theme of climate change effects.

Meaning: 'Adapt' means to change or adjust in response to new conditions, such as species altering their behavior or habitat in reaction to temperature changes.

Wrong options:

• prompt: Prompt means to cause or bring about an action, which does not fit the context of species changing in response to temperature; it implies an external trigger rather than an internal adjustment.
• adopt: Adopt means to take up or start to use something new, which does not accurately describe the process of species changing their behavior or habitat in response to environmental changes.
• adept: Adept refers to being skilled or proficient at something, which is irrelevant in this context as it does not relate to the behavior of marine species.

Correct answer: indicator

Explanation: The term 'indicator' is the correct choice as it signifies something that provides information about a condition or situation, fitting grammatically and contextually within the sentence. It highlights marine species as a measure of ocean warming, aligning with the scientific context of the passage.

Meaning: 'Indicator' means a sign or piece of information that indicates something, in this case, the sensitivity of marine species to climate change as a measure of ocean health.

Wrong options:

• administrator: Administrator refers to a person responsible for managing an organization or system, which does not relate to the context of marine species and their role in indicating environmental changes.
• emancipator: Emancipator means someone who frees others from restrictions, which is unrelated to the context of marine species and their role in indicating climate conditions.
• infiltrator: Infiltrator refers to someone or something that enters a place or organization secretly, which does not fit the context of marine species serving as indicators of environmental changes.

Correct answer: mobile

Explanation: The word 'mobile' is the correct answer as it describes the ability of fish to move freely and easily, fitting grammatically and contextually in the sentence. It emphasizes the adaptability of fish compared to land species, aligning with the discussion of their movement in response to environmental changes.

Meaning: 'Mobile' means capable of moving or being moved easily, highlighting the flexibility of fish in changing their locations in response to environmental factors.

Wrong options:

• fragile: Fragile means easily broken or damaged, which does not accurately describe the movement capabilities of fish in this context.
• juvenile: Juvenile refers to a young or immature stage of an organism, which is not relevant to the discussion of fish movement and adaptability.
• hostile: Hostile means unfriendly or antagonistic, which does not fit the context of fish behavior and their ability to move in response to environmental changes.

Correct answer: consistently

Explanation: The word 'consistently' is the correct choice as it indicates that populations have been measured in a reliable and steady manner over time, fitting grammatically and contextually within the sentence. It emphasizes the ongoing nature of the research on marine species across various habitats.

Meaning: 'Consistently' means in a way that does not change; reliably, indicating that measurements have been taken regularly and systematically over decades.

Wrong options:

• competently: Competently means in a capable or skilled manner, which does not fit the context of measuring populations as it does not convey the idea of regularity or reliability.
• potently: Potently refers to having great power or influence, which is unrelated to the context of measuring populations of marine species.
• intermittently: Intermittently means occurring at irregular intervals, which contradicts the idea of consistent measurement over time.