If a card is drawn from a well shuffled pack of cards, the probability of drawing a spade or a king is -

Answer: Option D

$$P\left(S\cup K\right)=$$   $$P\left(S\right)+$$  $$P\left(K\right)-$$  $$P\left(S\cap K\right),$$   (where S denotes spade and K denotes king.)
$$\begin{array}{rl}& P\left(S\cup K\right)=\frac{13}{52}+\frac{4}{52}-\frac{1}{52}\\ & =\frac{4}{13}\end{array}$$