What encourages a response be it internal or external of the body

Change in external environment is called stimuli. This stimuli encourage the response.

Explanation:

Response evoke internally when the stimuli is detected. Actually the internal environment fluctuates with external environment. Change in external environment try to bring out change in internal environment so to maintain Homeostasis is carried out.

answer; ///i believe the correct answer is (aids) acquired immune deficiency syndrome;

answer; i believe the correct answer is (anemia);