Concept: This question tests your knowledge of the cranial nerves, specifically the functions of the vagus nerve (Cranial Nerve X).

Why (A) is correct: The vagus nerve (Cranial Nerve X) is primarily involved in regulating various involuntary functions of the body, including those of the gastrointestinal tract, heart, and lungs. Tongue movements are primarily controlled by the hypoglossal nerve (Cranial Nerve XII), not the vagus nerve.

Why other options are wrong:

• (B) gastrointestinal movements: The vagus nerve plays a crucial role in stimulating peristalsis and secretion in the digestive system.
• (C) breathing: The vagus nerve influences respiratory rate and depth, and carries sensory information from the lungs.
• (D) cardiac movements: The vagus nerve is the main parasympathetic nerve to the heart, decreasing heart rate and contractility.

Common Mistake: Students often confuse the functions of different cranial nerves, especially those with overlapping or complex roles.

NEET Tip / Mnemonic: Remember the major functions of the vagus nerve as 'Vagus = Visceral'. It controls many involuntary visceral functions.

Correct Answer: (A)