Question

Which of the following is not a tautology ?

• A. $p\vee \sim p$
• B. $(p\Rightarrow q)\Rightarrow (\sim q\Rightarrow \sim p)$
• C. $p\vee \sim (q\wedge \sim q)$
• D. $p\wedge (q\vee \sim q)$

Answer 1

The correct option is D

$p\wedge (q\vee \sim q)$

A tautology is a statement which is always true. $p\wedge (q\vee \sim q)$ is false when p is false. Hence, it is not a tautology. Other statements are always true.