Meaning: 'Factors' means elements or conditions that contribute to a particular result, in this case, the amount of sleep required.

Wrong options:

• age: 'Age' is a singular noun and does not encompass the variety of influences on sleep, making it too narrow for this context.
• thing: 'Thing' is vague and informal, lacking specificity and clarity, which does not suit the formal tone of the text.
• category: 'Category' implies a classification, which does not accurately represent the multiple influences on sleep needs as described.

Correct answer: patterns

Explanation: The term 'patterns' is appropriate as it refers to the regularities or trends in sleeping behavior, which is the focus of the sentence regarding changes in sleep as one ages.

Meaning: 'Patterns' refers to the habitual ways in which sleep occurs, indicating how sleep behavior can evolve over time.

Wrong options:

• habits: 'Habits' suggests a more personal or behavioral aspect, which is less precise than 'patterns' in describing the overall changes in sleep behavior.
• time: 'Time' is too ambiguous and does not convey the idea of the structure or regularity of sleep, making it unsuitable in this context.
• hours: 'Hours' refers specifically to the duration of sleep rather than the nature of how sleep is experienced, which does not fit the context.

Correct answer: immune

Explanation: The word 'immune' correctly describes the system that protects the body from disease, fitting both grammatically and contextually as it relates to health and sleep.

Meaning: 'Immune' refers to the body's defense system against infections and diseases, highlighting the importance of sleep in maintaining health.

Wrong options:

• nervous: 'Nervous' pertains to the nervous system, which is not the focus here, as the sentence emphasizes health in relation to disease fighting.
• sleeping system: 'Sleeping system' is not a standard term and lacks clarity, making it inappropriate in a formal context.
• circulatory: 'Circulatory' refers to the system that circulates blood, which is unrelated to the context of sleep and health discussed in the passage.

Correct answer: important

Explanation: The word 'important' fits well as it emphasizes the significance of sleep quality, aligning with the context of the sentence that compares quality and quantity of sleep.

Meaning: 'Important' means having great significance or value, indicating that quality of sleep is as crucial as the amount of sleep one gets.

Wrong options:

• much: 'Much' is an adverb that does not convey the necessary meaning in this context, as it does not describe the significance of sleep.
• frequent: 'Frequent' describes occurrence rather than importance, making it irrelevant to the comparison being made in the sentence.
• trivial: 'Trivial' means of little value or importance, which contradicts the intended message about the significance of sleep quality.

Correct answer: identify

Explanation: The word 'identify' is appropriate as it means to recognize or determine the cause of sleep problems, fitting grammatically and contextually within the sentence.

Meaning: 'Identify' means to establish or recognize something, in this case, the underlying issues related to sleep problems.

Wrong options:

• determines: 'Determines' is a verb that implies a definitive conclusion, which does not fit the context of recognizing or diagnosing issues.
• help: 'Help' is too vague and does not convey the specific action of recognizing the cause of problems, making it less precise.
• solves: 'Solves' suggests a resolution rather than the process of recognizing an issue, which does not align with the context of the sentence.