ANATOMY

Detailed explanation-1: -The correct option is B excitability. Muscles of the body receive signals (stimuli) from brain. Excitability of muscles signifies how quickly they respond to stimuli. Quicker the response, more will be the excitability of muscles.

Detailed explanation-2: -Irritability. Irritability describes the ability to respond to a stimulus. Irritability is the ability to respond to a stimulus by initiating a nerve impulse. Irritability is one of the major characteristics of the neurons or nerve cells, which are the functional units of the nervous system.

Detailed explanation-3: -Contractility – ability to contract (make each cell shorter or longer) Irritability – each call has ability to contract on its own, to send out impulses to other cells without first being stimulated from another source.

Detailed explanation-4: -Final answer: The reaction to a stimulus is called response.