Concept: This question tests your understanding of the basic components and direction of impulse transmission in the nervous system, specifically distinguishing between afferent and efferent pathways.

Why (B) is correct: An afferent nerve fiber (also known as a sensory neuron) is responsible for transmitting sensory information from receptors (e.g., in the skin, eyes, ears) towards the Central Nervous System (CNS) for processing. Think of it as carrying information "to" the CNS.

Why other options are wrong:

• (A) C.N.S. to effector: This describes an efferent nerve fiber (motor neuron).
• (C) Receptor to effector: This bypasses the CNS and describes a reflex arc's direct connection, but the nerve fiber itself still goes via the CNS for processing or is part of a reflex arc where the afferent part goes to the CNS.
• (D) Effector to receptor: This direction of impulse transmission does not occur in the nervous system.

NEET Tip / Mnemonic: Remember "A"fferent = "A"rrives at CNS; "E"fferent = "E"xits CNS (or goes to "E"ffectors).

Correct Answer: (B)