Answer:
E. is the correct answer
Explanation:
C. An increase in A produces an increase in X.
This statement can be directly concluded from the description of the effects of hormone A on the activity of X in the problem.
A. An increase in X produces an increase in A
This statement can be concluded from the fact that A and X work in a positive feedback mechanism.
In a positive feedback mechanism, a stimulus produces a response (secretion of hormone A) which has an effect (increase in X) that increases the original stimulus. A cycle is created, in which secretion of A causes an increase of X, and the increase of X causes an increased secretion of A.
<u>To shut off the positive feedback cycle, an outside factor is required.</u>
