Correct option (D) Z
Explanation:
The path followed by nerve impulse in a reflex action is called reflex arc. The given figure shows reflex arc, where 'W' is effector (muscle in arm), 'X' is sensory neuron, 'Y' is motor neuron and 'Z' is interneuron (relay neuron). When our hand accidently touches a hot object, it is sensed by the receptors present in the skin of hand. This triggers nerve impulse in sensory neuron which is passed on to the intereuron in the spiral cord. The interneuron further passes on this impulse to the motor neuron. The motor neuron transmits the instruction to the effector in muscles of arm. The arm muscle contracts and pulls our hand away from the hot object.
