Concept: This question tests your understanding of the diverse and vital functions controlled by the human brain, encompassing both conscious and unconscious processes.

Why (D) is correct:

The human brain is the central processing unit of the nervous system and controls a vast array of bodily functions:

• a. Balance of the body: The cerebellum plays a crucial role in maintaining posture and equilibrium.
• b. Circadian rhythm of the body: The hypothalamus, specifically the suprachiasmatic nucleus (SCN), acts as the body's master clock, regulating sleep-wake cycles and other circadian rhythms.
• c. Human behaviour: Complex behaviours, emotions, memory, and decision-making are primarily controlled by the cerebrum, especially the cerebral cortex.
• d. Functioning of heart and kidneys: The medulla oblongata (part of the brainstem) regulates vital involuntary functions like heart rate and breathing. While kidneys are primarily regulated by hormones and their own intrinsic mechanisms, the brain (hypothalamus, pituitary) influences kidney function through ADH secretion and blood pressure regulation.

Therefore, all listed functions are, directly or indirectly, controlled or influenced by the human brain.

Why other options are wrong:

Options A, B, and C are incorrect because they exclude one or more functions that are indeed controlled by the brain.

Common Mistake: Students might overlook the brain's indirect control over organs like the heart and kidneys, thinking they are purely autonomous. Remember that the brainstem and hypothalamus exert significant regulatory control over these vital organs.

NEET Tip: Think of the brain as the ultimate coordinator. If a bodily function requires regulation, integration, or conscious thought, the brain is involved. Different parts of the brain specialize in different functions (e.g., cerebellum for balance, cerebrum for thought, medulla for vital reflexes).

Correct Answer: (D)