A.I. Explanation:

Correct answer: downturn

Explanation: The word 'downturn' fits grammatically as a noun that describes a decline in economic conditions, which aligns with the context of middle-class parents facing financial pressures. It maintains the logical flow of the sentence, indicating the reason for their shift in educational choices.

Meaning: 'Downturn' refers to a decline or decrease, particularly in economic terms.

Wrong options:

• return: 'Return' is a verb that does not fit the context of describing a financial situation.
• reserved: 'Reserved' is an adjective that does not relate to economic conditions and does not fit grammatically here.
• popular: 'Popular' is an adjective that describes something well-liked, which does not fit the context of financial pressures.
• explaining: 'Explaining' is a gerund that does not serve as a noun to describe the economic situation.
• imitating: 'Imitating' is a gerund that does not relate to the context of financial pressures and does not fit grammatically.

Correct answer: popular

Explanation: The term 'popular' is an adjective that describes the Good Schools Guide as being well-liked and widely used among fee-paying families. This fits grammatically and contextually, as it highlights the guide's significance in the educational landscape.

Meaning: 'Popular' means well-liked or favored by many people.

Wrong options:

• return: 'Return' is a verb that does not fit as a descriptor for the reference book.
• downturn: 'Downturn' is a noun that describes a decline, which does not fit as an adjective for the guide.
• explaining: 'Explaining' is a gerund that does not serve as an adjective and does not fit in this context.
• imitating: 'Imitating' is a gerund that does not describe the guide and is not appropriate here.
• reserved: 'Reserved' is an adjective that implies something is kept back or set aside, which does not fit the context of popularity.

Correct answer: explaining

Explanation: The word 'explaining' is a gerund that serves as the subject of the clause, indicating the action of providing reasons for the increase in state schools featured in the guide. It fits grammatically and logically within the context of the sentence.

Meaning: 'Explaining' refers to the act of making something clear or understandable.

Wrong options:

• return: 'Return' is a verb that does not fit as a subject in this context.
• reserved: 'Reserved' is an adjective that does not relate to the action of providing information.
• popular: 'Popular' is an adjective that does not fit as a subject and does not convey the action of explaining.
• downturn: 'Downturn' is a noun that does not fit as a subject in this context.
• imitating: 'Imitating' is a gerund that does not relate to the context of providing explanations.