Correct choice is (c) Competitive inhibition
Easiest explanation: In competitive inhibition, the inhibitor is having structural similarity to substrate, and often is a reaction product. As lactose and galactose have structural similarity, they exhibit competitive inhibition. Substrate inhibition is a case uncompetitive inhibition. Uncompetitive inhibition occurs wherein one substrate is competitive and other substrate is non-competitive with respect to the enzyme. Mixed inhibition is said to occur when both enzyme-inhibitor and enzyme-substrate-inhibitor complexes are formed.