A competitive inhibitor, competes with the substrate, for the substrate binding site of enzymes due to its
a)	Structural similarity with substrate
b)	Molecular weight similarity with substrate
c)	Both (a) and (b)
d)	Larger size than that of substrate

(a)

When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate-binding site of the enzyme.

Consequently, the substrate cannot bind and as a result, the enzyme action declines, ., inhibition of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure. Such competitive inhibitors are often used in the control of bacterial pathogens