_______ is not a part of an expert system.
A knowledge base is not a part of an expert system.
A knowledge-based system (KBS) is a computer program that reasons and uses a knowledge base to solve complex problems. A more specific definition of the domain restricts it to expert systems (ES) called knowledge-based systems.
Expert system:-
In artificial intelligence, an expert system is a computer system that emulates the decision-making ability of a human expert. Expert systems are designed to solve complex problems by reasoning through bodies of knowledge, represented mainly as if-then rules rather than through conventional procedural code.