Statements about Enzyme Inhibitor Drugs are given below:
(A) There are Competitive and Non-competitive inhibitor drugs.
(B) These can bind at the active sites and allosteric sites.
(C) Competitive Drugs are allosteric site blocking drugs.
(D) Non-competitive Drugs are active site blocking drugs.
Choose the correct answer from the options given below:

Let us evaluate each statement about enzyme inhibitor drugs:

(A) "There are Competitive and Non-competitive inhibitor drugs."

This is correct. Enzyme inhibitors are broadly classified into competitive and non-competitive inhibitors.

(B) "These can bind at the active sites and allosteric sites."

This is correct. Competitive inhibitors bind at the active site of the enzyme, while non-competitive inhibitors bind at the allosteric site (a site different from the active site). So collectively, enzyme inhibitor drugs can bind at both types of sites.

(C) "Competitive Drugs are allosteric site blocking drugs."

This is incorrect. Competitive inhibitors block the active site, not the allosteric site. They compete with the substrate for binding at the active site.

(D) "Non-competitive Drugs are active site blocking drugs."

This is incorrect. Non-competitive inhibitors bind at the allosteric site, not the active site. They change the shape of the enzyme so that the substrate cannot fit into the active site.

Statements (C) and (D) have the descriptions interchanged — each incorrectly describes the other type of inhibitor.

Therefore, only statements A and B are correct, and the answer is Option C: A, B only.