Answer:
a - Enzyme
b- Active site
c- Substrate
d- Products
Step-by-step explanation:
A substance which catalyses a chemical reaction is called enzyme. It does not use in a reaction but speeds up a chemical reaction. Enzymes are also called biocatalyst. An enzyme binds to the active site of the substrate to form the substrate-enzyme complex. Later substrate changed into products and enzyme released from the complex unused.