Let $p$ and $q$ be two statements.Then $\sim( p \wedge( p \Rightarrow \sim q ))$ is equivalent to

Which of the following Boolean expression is a tautology ?

Let $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ be four non-empty sets. The contrapositive statement of "If $\mathrm{A} \subseteq \mathrm{B}$ and $\mathrm{B} \subseteq \mathrm{D},$ then $\mathrm{A} \subseteq \mathrm{C}^{\prime \prime}$ is 

Which of the following statements is a tautology?

Negation of the statement $(p \vee r) \Rightarrow(q \vee r)$ is :

The contrapositive of the statement "If I reach the station in time, then I will catch the train" is