Which statement about biphasic sleep pattern is true for adulthood?

• A. It may re-emerge
• B. It becomes monophasic
• C. It disappears
• D. It remains unchanged

Answer: (A)

Biphasic sleep refers to two distinct sleep periods within a 24-hour day, with a wakeful interval in between. In adulthood, the typical pattern is a single, consolidated sleep block, but the system allowing two sleep blocks can reappear under certain conditions. Factors like aging, changes in work schedules, cultural practices, or natural circadian shifts can bring back a split sleep pattern in adults. This makes the statement that it may re-emerge the best fit, since it acknowledges that adult sleep patterns are not fixed and can move between monophasic and biphasic over a person’s life.

The other possibilities don’t fit as broadly: sleep does not necessarily become permanently monophasic, disappear altogether, or stay unchanged for all adults.