A.I. Explanation:

Correct answer: support

Explanation: The verb 'support' is used here to indicate that coral reefs provide sustenance or habitat for marine life. It fits grammatically as it is in the present tense, matching the overall tense of the sentence, and contextually aligns with the idea of coral reefs being vital to marine ecosystems.

Meaning: 'Support' means to provide the necessary conditions for something to exist or thrive.

Wrong options:

• double: 'Double' is a verb that means to increase twofold, which does not fit the context of providing sustenance.
• single: 'Single' is an adjective that refers to one, which does not relate to the action of providing support.
• rattle: 'Rattle' is a verb that means to make a series of short, sharp noises, which is unrelated to the context of marine life.
• surprisingly: 'Surprisingly' is an adverb that indicates something unexpected, which does not fit as a verb in this context.
• forecast: 'Forecast' is a verb that means to predict or estimate, which does not align with the idea of providing support.

Correct answer: surprisingly

Explanation: The adverb 'surprisingly' modifies the clause, indicating that the fact that coral reefs are a favorite pursuit for divers is unexpected. It fits grammatically as it provides an adverbial context to the sentence, enhancing the meaning of the statement.

Meaning: 'Surprisingly' means in a way that causes surprise or is unexpected.

Wrong options:

• support: 'Support' is a verb that does not fit grammatically as it does not modify the clause appropriately.
• double: 'Double' is a verb that does not fit as it does not serve as an adverb to modify the statement about divers.
• single: 'Single' is an adjective that does not fit the context of modifying the clause about divers.
• rattle: 'Rattle' is a verb that does not relate to the context of the sentence and does not fit grammatically.
• forecast: 'Forecast' is a verb that does not serve as an adverb and does not fit the context.

Correct answer: double

Explanation: The verb 'double' indicates an increase in quantity, which fits the context of the sentence discussing the expected growth in the number of people relying on coral reefs. It is in the present tense, aligning with the overall tense of the passage.

Meaning: 'Double' means to increase to twice the amount.

Wrong options:

• support: 'Support' is a verb that does not fit the context of predicting an increase in numbers.
• single: 'Single' is an adjective that does not relate to the action of increasing or predicting growth.
• rattle: 'Rattle' is a verb that does not fit the context of discussing numbers or predictions.
• surprisingly: 'Surprisingly' is an adverb that does not fit as a verb in this context.
• forecast: 'Forecast' is a verb that means to predict, but it does not fit grammatically in the structure of the sentence.

Correct answer: arrive

Explanation: The verb 'arrive' is used here to indicate reaching a conclusion or scenario. It fits grammatically as it is in the present tense and contextually aligns with the idea of coming to a realization about potential future scenarios regarding coral reefs.

Meaning: 'Arrive' means to reach a destination or conclusion.

Wrong options:

• support: 'Support' is a verb that does not fit the context of reaching a conclusion about scenarios.
• double: 'Double' is a verb that does not relate to the action of arriving at scenarios.
• single: 'Single' is an adjective that does not fit the context of the sentence.
• rattle: 'Rattle' is a verb that does not relate to the context of discussing scenarios or conclusions.
• surprisingly: 'Surprisingly' is an adverb that does not fit as a verb in this context.
• forecast: 'Forecast' is a verb that means to predict, but it does not fit grammatically in the structure of the sentence.