Meaning: Disproportionate means unequal or not in proportion to something else.

Wrong options:

• reflects: Reflects is a verb that means to show or demonstrate, which does not fit as it does not describe the amount of sleep lost.
• decline: Decline is a noun that refers to a decrease, which does not fit as it does not describe the nature of the sleep loss.
• dispassionate: Dispassionate is an adjective meaning unemotional or detached, which does not relate to the context of sleep loss.
• stage: Stage is a noun that refers to a particular point or period in a process, which does not fit as it does not describe the nature of the sleep loss.

Correct answer: decline

Explanation: The term 'decline' is a noun that refers to a decrease or reduction. In this context, it describes the reduction in sleep quality and quantity for adults, fitting grammatically as it serves as the subject of the sentence.

Meaning: Decline means a decrease or reduction in something.

Wrong options:

• persists: Persists is a verb that means to continue or endure, which does not fit as it does not describe the nature of the sleep quality and quantity.
• reflects: Reflects is a verb that means to show or demonstrate, which does not fit as it does not describe a decrease in sleep.
• dispassionate: Dispassionate is an adjective meaning unemotional or detached, which does not relate to the context of sleep quality and quantity.
• stage: Stage is a noun that refers to a particular point or period in a process, which does not fit as it does not describe a decrease.

Correct answer: persists

Explanation: The word 'persists' is a verb that means to continue to exist or endure over a prolonged period. In this context, it indicates that the decline in sleep quality and quantity continues until the child is about six years old, fitting grammatically as it describes the action of the decline.

Meaning: Persists means to continue or endure over time.

Wrong options:

• decline: Decline is a noun that refers to a decrease, which does not fit as it does not describe the action of continuing.
• reflects: Reflects is a verb that means to show or demonstrate, which does not fit as it does not indicate continuation.
• dispassionate: Dispassionate is an adjective meaning unemotional or detached, which does not relate to the context of the action of sleep quality.
• stage: Stage is a noun that refers to a particular point or period in a process, which does not fit as it does not describe the action of continuing.