A computer system that uses a set of rules to make decisions based on input data is generally known as which of the following?

An expert system is a type of computer system designed to simulate the judgment and behavior of a human or an organization that has expert-level expertise in a specific domain. It utilizes a set of rules, often derived from human experts, to make decisions and solve problems based on given input data. The rules function similarly to "if-then" statements, enabling the system to process specific information and arrive at a conclusion, much like a human expert would.

In contrast, while decision trees are useful for making decisions based on data attributes and outcomes, they do not inherently use a set of rules in the same structured way as an expert system. Fuzzy logic systems deal with reasoning that is approximate rather than fixed and exact, addressing uncertainty and vagueness in decision-making. Bayesian networks provide a probabilistic graphical model that represents a set of variables and their conditional dependencies using Bayesian inference, which diverges from the rule-based approach of expert systems.

Thus, the defining characteristic of an expert system—specifically its rule-based decision-making—makes it the appropriate choice for this question.