Meaning: 'Enough' means a sufficient amount or degree, indicating that many Americans do not get the required amount of sleep for their health.

Wrong options:

• necessary: 'Necessary' implies something that is essential, but it does not convey the idea of quantity, making it unsuitable in this context.
• such: 'Such' is used to refer to something previously mentioned or of a particular kind, which does not fit the context of measuring sleep quantity.
• sufficient: 'Sufficient' is similar to 'enough' but is more formal and does not fit as smoothly in the conversational tone of the sentence.

Correct answer: regardless of

Explanation: The phrase 'regardless of' is used to indicate that something is true without being affected by other factors, which fits the context of comparing sleep habits irrespective of socioeconomic status.

Meaning: 'Regardless of' means without considering or being influenced by something, emphasizing that the disparity in sleep habits exists despite socioeconomic factors.

Wrong options:

• compared to: 'Compared to' suggests a direct comparison, which does not convey the idea of independence from socioeconomic status as effectively as 'regardless of'.
• no matter: 'No matter' is a phrase that indicates indifference but is less formal and does not fit the grammatical structure as well as 'regardless of'.
• nevertheless: 'Nevertheless' implies a contrast or concession, which does not align with the intended meaning of showing independence from socioeconomic status.

Correct answer: attributed

Explanation: The word 'attributed' is correctly used to indicate that the researchers assigned the cause of the disparity to specific factors, fitting both grammatically and contextually in the sentence.

Meaning: 'Attributed' means to regard something as being caused by someone or something, indicating that the researchers linked the disparity to racism and stress.

Wrong options:

• preserved: 'Preserved' means to maintain something in its original state, which does not fit the context of explaining causes.
• disclosed: 'Disclosed' means to reveal or make known, which does not convey the idea of assigning a cause as effectively as 'attributed'.
• separated: 'Separated' means to set apart or divide, which is unrelated to the context of explaining the cause of the disparity.

Correct answer: cause

Explanation: The word 'cause' fits grammatically and contextually as it indicates that sleep disparities are a factor leading to social and health inequities, aligning with the overall message of the sentence.

Meaning: 'Cause' refers to something that brings about an effect or a result, indicating that sleep disparities contribute to broader issues of inequity.

Wrong options:

• pivot: 'Pivot' suggests a central point of change, which does not accurately describe the relationship between sleep disparities and health inequities.
• progression: 'Progression' implies a process of development or advancement, which does not fit the context of establishing a direct relationship as a cause does.
• result: 'Result' indicates an outcome rather than a contributing factor, making it the opposite of what is intended in this context.

Correct answer: determinants

Explanation: The word 'determinants' is appropriate as it refers to factors that influence or determine outcomes, fitting well within the context of discussing the structural factors affecting sleep health.

Meaning: 'Determinants' means factors that decisively affect the nature or outcome of something, indicating that these are the underlying causes of poor sleep.

Wrong options:

• stems: 'Stems' implies a source or origin but does not convey the broader concept of influencing factors as 'determinants' does.
• deterrents: 'Deterrents' refers to things that discourage or prevent actions, which does not align with the context of discussing factors that influence sleep health.
• symbols: 'Symbols' represent ideas or concepts but do not relate to the factors affecting sleep, making it irrelevant in this context.