The correct answer is (a) Reaction specificity
To explain: In the above diagram, an example for reaction specificity is shown. The type of specificity in which the enzyme is specific to a particular reaction, but not substrate and catalyzes only one type of reaction is referred to reaction specificity. As shown in the diagram, pyruvate can undergo several reactions. But each reaction is catalyzed by a separate enzyme, which catalyzes only that reaction and none other. Hence it is a perfect example for reaction specificity.