A.I. Explanation:

Correct answer: shortage

Explanation: The word 'shortage' fits grammatically as a noun that describes a lack of something, in this case, working-age populations. It aligns with the context of discussing demographic challenges and potential solutions through migration.

Meaning: 'Shortage' refers to a situation where there is not enough of something, indicating a deficiency in working-age individuals.

Wrong options:

• source: 'Source' is a noun that refers to the origin of something, which does not fit the context of describing a lack of working-age populations.
• benefit: 'Benefit' is a verb that means to gain or receive an advantage, which does not fit as it does not describe a lack or deficiency.
• promote: 'Promote' is a verb that means to support or encourage, which does not fit as it does not describe a lack of working-age populations.
• weakness: 'Weakness' is a noun that refers to a lack of strength or a fault, but it does not specifically indicate a shortage of working-age individuals.
• origin: 'Origin' is a noun that refers to the beginning or source of something, which does not fit the context of describing a lack of working-age populations.

Correct answer: benefit

Explanation: The term 'benefit' serves as a verb that indicates the action of gaining an advantage, which is contextually appropriate as it describes the positive outcomes for both migrant-sending and receiving countries.

Meaning: 'Benefit' means to gain an advantage or profit from something.

Wrong options:

• source: 'Source' is a noun that refers to the origin of something, which does not fit as it does not convey an action of gaining advantage.
• shortage: 'Shortage' is a noun that describes a lack of something, which does not fit as it does not indicate a positive outcome or action.
• promote: 'Promote' is a verb that means to support or encourage, but it does not directly convey the idea of gaining an advantage in this context.
• cooperate: 'Cooperate' is a verb that means to work together, which does not fit as it does not indicate a direct benefit or advantage.
• weakness: 'Weakness' is a noun that refers to a lack of strength or a fault, which does not fit as it does not convey a positive outcome.

Correct answer: cooperate

Explanation: The word 'cooperate' is a verb that indicates the action of working together towards a common goal, which is essential in the context of nations needing to collaborate to address migration challenges.

Meaning: 'Cooperate' means to work jointly with others towards a common goal.

Wrong options:

• source: 'Source' is a noun that refers to the origin of something, which does not fit as it does not convey an action of collaboration.
• shortage: 'Shortage' is a noun that describes a lack of something, which does not fit as it does not indicate an action of working together.
• benefit: 'Benefit' is a verb that means to gain an advantage, but it does not fit as it does not convey the idea of collaboration among nations.
• promote: 'Promote' is a verb that means to support or encourage, which does not fit as it does not indicate the action of working together.
• weakness: 'Weakness' is a noun that refers to a lack of strength or a fault, which does not fit as it does not convey an action.

Correct answer: source

Explanation: The term 'source' is a noun that refers to the origin or starting point of something, which is contextually appropriate as it describes countries that provide migrants.

Meaning: 'Source' refers to the place or origin from which something comes, in this case, countries that are the origin of migrants.

Wrong options:

• shortage: 'Shortage' is a noun that describes a lack of something, which does not fit as it does not indicate a place of origin.
• benefit: 'Benefit' is a verb that means to gain an advantage, which does not fit as it does not describe a country or origin.
• promote: 'Promote' is a verb that means to support or encourage, which does not fit as it does not describe a place or origin.
• cooperate: 'Cooperate' is a verb that means to work together, which does not fit as it does not describe a country or origin.
• weakness: 'Weakness' is a noun that refers to a lack of strength or a fault, which does not fit as it does not describe a country or origin.