Answer;
D. A would increase; B and C would decrease
Explanation;
-Enzymes can be regulated by other molecules that either increase or reduce their activity. Molecules that increase the activity of an enzyme are called activators, while molecules that decrease the activity of an enzyme are called inhibitors.
-Inactivating enzyme 1 mean that the concentrations of molecules A would increase because enzymes is not acting on it to produce product B, which is the substrate for enzyme 2, thus both B and C would decrease relative to what they would be if the pathway were fully functional.