Assertion (A): Nothing is an offense which is done by a person who, at the time of doing it by reason of unsoundness of mind, is incapable of knowing the nature of the act.

Reason (R): Mistake of fact is a good defense, and Mistake of Law is no defense.

Correct option is B

The assertion (A) refers to Section 84 of the IPC, which deals with acts committed by a person of unsound mind, making such acts not an offense if the person is incapable of understanding their nature. The reason (R) is also correct; however, it explains a different legal principle related to defenses of mistake of fact and mistake of law. Therefore, while both statements are true, the reason does not directly explain the assertion.
Information Booster

Section 84 of IPC provides the legal defense of insanity, meaning that a person cannot be held criminally liable if, at the time of the act, they were of unsound mind and incapable of understanding the nature of their act.
Additional Knowledge
· Mistake of Fact: A factual error that can be a valid defense under Section 76 or Section 79 IPC if the act was done under a misconception of fact.
· Mistake of Law: Generally, ignorance of the law is not an excuse and cannot be used as a defense.