Reduction to absurdity is a method of proving the authenticity of a topic  by first determining the falseness of the topic in contradiction with the original topic, and then inferring the truth from the falseness according to the law of excluded middle, so as to indirectly determine the authenticity of the topic.
According to the above definition, which of the followings does not belong to the reduction to absurdity?
A person is guilty of illegal income. If he is not guilty, he should can tell the source of all his income, but he can't tell it.