a)If p is T and q is T
then $p \vee q $ is T
$\therefore p \vee q$ cannot be a contradiction
b)If p is T and q is T
then $p \wedge q $ is T
$\therefore p \wedge q$ cannot be a contradiction
c)If p is T then $\sim p$ is F
then $p \vee \sim p$ is T
If p is F then $\sim p$ is T.
then $p \vee \sim p$ is T
$\therefore p \vee \sim p$ not a contradiction
d)If p is T then $\sim p$ is F
then $p \wedge \sim p$ is F
If p is T then $\sim p$ is F.
$\therefore p \wedge \sim p$ is contradiction
Hence 4 is a correct answer.