Use the Following Information to Answer the Corresponding Questions)

Use the following information to answer the corresponding questions) .
A series of enzymes catalyze the reaction X -Y -Z -A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.
-What is substance X?

A) the product
B) a substrate
C) a coenzyme
D) an intermediate
E) an allosteric inhibitor