In a Positive-Feedback System Where Hormone a Alters the Amount

In a positive-feedback system where hormone A alters the amount of protein X

A) an increase in A always produces an increase in X.
B) an increase in X always produces a decrease in A.
C) a decrease in A always produces an increase in X.
D) a decrease in X always causes a decrease in A.
E) it is impossible to predict how A and X affect each other.