Answer is C) $\dfrac{7}{16}$
Probability of obtaining head$= \text{Probability of picking first coin} \times \text{Probability of getting head on first coin}$
$+ \text{Probability of picking second coin}\times \text{Probability of getting head on second coin}$
$ = \left(\dfrac{1}{2}\times \dfrac{5}{8}\right) +\left( \dfrac{1}{2}\times \dfrac{1}{4}\right) = \dfrac{7}{16}.$