Explanation

(c)
Probability of getting a king $= \frac{4}{52} = \frac{1}{13}$
Probability of getting a spade $= \frac{13}{52} = \frac{1}{4}$
Probability of getting king and a spade $= \frac{1}{52}$
$\therefore P$(king or spade)$= P$(king)+$P$(spade)$- P$(king and spade)
$= \frac{1}{13} + \frac{1}{4} - \frac{1}{52} = \frac{4 + 13 - 1}{52} = \frac{16}{52} = \frac{4}{13}$