A process cannot be totally reversible if it has: a. Heat transfer through a temperature difference b. Frictionless surfaces C. A single pure substance d. Internal reversibility

a. Heat transfer a temperature difference

Explanation:

If system is not in thermal equilibrium then there will be ir-reversibility. We know that when system have temperature difference then heat transfer take place. So process can not be reversible process.

Friction less surface can be reversible process if all other parameter are ideal.

So from this our answer will be a.