Apeacock spreading its tail to attract a mate is sending stimulus

The correct answer is:

external

Explanation:

Physiology Something that can obtain or provoke a physiological answer in a cell, a tissue, or an organism. A stimulus can be internal or external. Sense organs, such as the ear, and sensory receptors, such as those in the skin, are receptive to outside stimuli such as noise and touch. A stimulus can be external, indicating it happens outside the organism.

answer; (phospholipid);

"do a testcross with a homozygous recessive plant."