Neuron Identification in Reflex Arc

Steps:

• Recall sensory neurons carry signals from receptors to CNS, with cell body off the axon.
• Identify relay neurons in CNS, connecting sensory to motor with branched dendrites.
• Recognize motor neurons transmit from CNS to effectors, with long axon and cell body inside CNS.
• Match diagram labels: 1 shows motor features (efferent path), 2 relay (interneuron), 3 sensory (afferent from periphery).

Why A is correct:

• A aligns with definitions: motor neurons exit CNS (label 1), relays connect within CNS (2), sensory enter CNS (3).

Why the others are wrong:

• B mislabels initial efferent as sensory, ignoring signal direction from CNS.
• C starts with relay, but diagrams begin with motor or sensory endpoints.
• D swaps sensory and relay, violating CNS interneuron role.

Not enough information: Diagram not provided, assuming standard labeling.

Final answer: A