The correct answer is: B. Substitution
Backward chaining is a search technique used in artificial intelligence to find a solution to a problem. It starts with the goal and works backwards, trying to
find the facts that would prove the goal.Substitution is a rule of inference that allows us to replace one expression with another, provided that the two expressions are logically equivalent. In backward chaining, we use substitution to replace a goal with one of its subgoals. This allows us to break the problem down into smaller and smaller subproblems until we reach a problem that is easy to solve.
Conjuncts are two or more statements that are joined together with the word “and.” In backward chaining, conjuncts are used to represent the conditions that must be true in order for the goal to be true.
Composition of substitution is a rule of inference that allows us to combine two substitutions. In backward chaining, we use composition of substitution to combine two subgoals into a single subgoal. This allows us to solve more complex problems.
None of the mentioned is not the correct answer because it does not represent any of the rules of inference that are used in backward chaining.