Meaning: 'Medical' refers to anything related to the science of medicine, particularly in terms of health and healthcare technology.

Wrong options:

• individuals: 'Individuals' is a noun referring to single persons, which does not describe a type of technology.
• relevant: 'Relevant' is an adjective that describes the importance of something, not applicable to technology.
• scale: 'Scale' is a noun that refers to the size or level of something, which does not fit the context of technology.
• found: 'Found' is a verb that means to establish or set up, which does not relate to technology in this context.
• range: 'Range' is a noun that refers to a variety or extent, which does not describe technology.
• diverse: 'Diverse' is an adjective that describes variety, but it does not fit as a descriptor for technology.

Correct answer: range

Explanation: The term 'range' fits grammatically as it refers to a variety of causes. It is contextually appropriate as it indicates the breadth of factors contributing to population aging.

Meaning: 'Range' refers to the extent or variety of something, in this case, the different causes affecting population changes.

Wrong options:

• individuals: 'Individuals' does not fit as it refers to single persons, not a variety of causes.
• relevant: 'Relevant' is an adjective that describes importance, which does not apply to the concept of variety.
• scale: 'Scale' refers to size or extent, which does not convey the idea of variety in causes.
• found: 'Found' is a verb that does not relate to the concept of variety or causes.
• medical: 'Medical' describes health-related aspects, which does not fit the context of a variety of causes.
• diverse: 'Diverse' is an adjective that describes variety but does not fit as a noun to describe causes.

Correct answer: relevant

Explanation: The word 'relevant' fits grammatically as an adjective describing the issue of aging populations. It is contextually appropriate as it emphasizes the importance of the topic in relation to current societal challenges.

Meaning: 'Relevant' means closely connected or appropriate to what is being discussed, highlighting the significance of aging populations.

Wrong options:

• individuals: 'Individuals' does not fit as it refers to single persons, not the significance of an issue.
• scale: 'Scale' refers to size or extent, which does not apply to the importance of the issue.
• medical: 'Medical' describes health-related aspects, which does not fit the context of relevance to aging populations.
• found: 'Found' is a verb that does not relate to the importance of an issue.
• range: 'Range' refers to variety, which does not convey the significance of the topic.
• diverse: 'Diverse' is an adjective that describes variety but does not fit as a descriptor for the relevance of an issue.

Correct answer: individuals

Explanation: The term 'individuals' fits grammatically as a plural noun referring to people. It is contextually appropriate as it discusses the need for people to work longer before retirement.

Meaning: 'Individuals' refers to single persons, emphasizing the focus on people in the context of retirement and work.

Wrong options:

• relevant: 'Relevant' is an adjective that does not fit as a noun referring to people.
• scale: 'Scale' refers to size or extent, which does not apply to people in this context.
• medical: 'Medical' describes health-related aspects, which does not fit the context of discussing people.
• found: 'Found' is a verb that does not relate to the subject of individuals needing to work.
• range: 'Range' refers to variety, which does not apply to the context of people working longer.
• diverse: 'Diverse' is an adjective that describes variety but does not fit as a noun referring to people.

Correct answer: diverse

Explanation: The word 'diverse' fits grammatically as an adjective describing the effects of aging populations. It is contextually appropriate as it indicates the variety of effects experienced across different countries.

Meaning: 'Diverse' means showing a great deal of variety; it highlights the different impacts of aging populations in various contexts.

Wrong options:

• individuals: 'Individuals' does not fit as it refers to single persons, not the effects of aging populations.
• relevant: 'Relevant' is an adjective that describes importance, which does not apply to the variety of effects.
• scale: 'Scale' refers to size or extent, which does not convey the idea of variety in effects.
• medical: 'Medical' describes health-related aspects, which does not fit the context of effects of aging populations.
• range: 'Range' refers to variety but does not fit as an adjective describing effects.
• found: 'Found' is a verb that does not relate to the description of effects.