Final answer:
The suprachiasmatic nucleus (SCN) is the body's 'master clock' located in the hypothalamus, controlling circadian rhythms and synchronizing the internal clock with the external light cycle. The option (B) is correct.
Step-by-step explanation:
The suprachiasmatic nucleus (SCN) serves as the body's "master clock" and is responsible for controlling circadian rhythms. Located in the hypothalamus, the SCN receives direct input from the eyes, which sense the level of light in the environment.
This light information enables the SCN to synchronize the body's internal clock with the day-night cycle. Disorders of the circadian rhythm can have various impacts on an individual's health, emphasizing the critical role of the SCN in maintaining normal sleep-wake patterns and overall homeostasis. Therefore, option (B) is correct.