Final answer:
The correct answer is option a. heuristic.
Step-by-step explanation:
The knowledge base component of an expert system must include heuristic knowledge, which consists of rules related to a problem or discipline. Heuristic knowledge involves mental shortcuts or rules of thumb that provide a method for problem-solving which is not necessarily optimal but is efficient. This type of knowledge is paramount in creating systems that can emulate decision-making in a way that mimics human thought processes.
Heuristics are part of cognitive psychology and are crucial in quick decision-making. As opposed to algorithms which require a sequential process for problem-solving, heuristics allow for more flexibility and are often faster, although they might not always yield the most accurate or optimal result. These heuristic methods are implemented as sets of rules in expert systems to facilitate the solving of complex problems and are a key component of artificial intelligence.