Idk anything right now, I’ll comment the answer later
The answer is; A
The active site of the enzyme is bound by a substrate and probably the enzyme catalyzes a hydrolysis reaction. The poison mimics the substrate and competes with the substrate for the active site of the enzyme. The poison may bind permanently to the enzyme rendering the enzyme unavailable for other substrates. This could make a particular biochemical reaction, in which the enzyme is involved, to reduce drastically hence threatening life.
The answer to the blank i think is bond im not 100% sure though..
This would be considered a mutation.