Question

what is a reflex?
o an automatic, involuntary response to a specific stimulus
o a signal sent on a motor neuron to initiate a voluntary movement
o a type of neuromuscular junction, found on smooth muscles

Explanation:

A reflex is an innate, unlearned, involuntary reaction to a particular stimulus, like the knee - jerk reflex. It does not involve conscious thought or voluntary control.

Answer:

An automatic, involuntary response to a specific stimulus