Step 1: Identify the material required for crockery.
Crockery requires materials that are heat resistant, hard, and chemically inert.
Step 2: Properties of melamine.
Melamine forms a thermosetting polymer (melamine–formaldehyde resin) which is hard, glossy, and heat resistant.
Step 3: Eliminate other options.
HDPE is used for containers, while Buna-S and Buna-N are synthetic rubbers.
Step 4: Conclusion.
Thus, melamine is used to make crockeries.