Aseries 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. with respect to the enzyme that converts x to y, substance a functions asa. a coenzyme. b. an allosteric inhibitor. c. the substrate. d. an intermediate. e. a competitive inhibitor.

Option B, an allosteric inhibitor.

Explanation:

As the enzyme activity decreases, it is not possible for A to be a coenzyme (most likely would increase the enzyme activity), a substrate (increases activity of enzyme by Le Chatler's principle) or an intermediate (no effect). A is unlikely to be a competitive inhibitor as this would not decrease the activity of the enzyme, only  reduce the rate of conversion of substrate to product. A is most likely an allosteric inhibitor which binds to another site on the enzyme (other than the active site), resulting in a change in conformation of the enzyme which reduces the enzymatic activity.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.