Question

Which is an example of an internal stimulus?

A.
a sudden change of air temperature

B.
an artificial light that attracts insects

C.
an increase in the amount of water available to a plant

D.
a decrease in oxygen levels in the blood during exercise

Answer 1

D. A decrease in oxygen levels in the blood during exercise.

Step-by-step explanation:

Trus me

Answer 2

D thats the only answer that is internal