A tautology is a statement that is true no matter what the truth values of its constituent statements are. Decide which of the following are tautologies.
(a) $(P$ or $(\operatorname{not} P))$
(b) $(P$ and $(\operatorname{not} P))$
(c) $(P \Rightarrow(\operatorname{not} P))$
(d) $(((P \Rightarrow Q)$ or $(Q \Rightarrow P))$ and $(\operatorname{not} Q))$