MICROANATOMY

Detailed explanation-1: -The correct option is A Stimulus. Something that causes a response is known as stimulus.

Detailed explanation-2: -The ability of an organism to respond to external stimuli is called sensitivity.

Detailed explanation-3: -A stimulus is anything that can trigger a physical or behavioral change. The plural of stimulus is stimuli. Stimuli can be external or internal. An example of external stimuli is your body responding to a medicine.

Detailed explanation-4: -Stimulus is an event or any change in the external environment that evokes a specific functional reaction in an organ or tissue. stimulus can be internal or external. Sense organs, such as the ear, and sensory receptors, such as those in the skin, are sensitive to external stimuli such as sound and touch.