In a classic Conan Doyle story. Sherlock Holmes solves a crime mystery by recognizing that a guard dog didn't bark. Therefore. the dog must have known the perpetrator. Holmes' reasoning goes like this: if the guard dog doesn't know a person. then it barks. The dog didn't bark. Therefore, it knew the person. Which rule of inference is being used here?

Addition. Addition

Simplification. Simplification

Conjunction. Conjunction

Modus Ponens. Modus Ponens

Hypothetical Syllogism. Hypothetical Syllogism

Disjunctive Syllogism. Disjunctive Syllogism

Modus Tollens. Modus Tollens

Resolution. Resolution