A family has 4 children. A child is selected at random from the family. Assuming that there are equal number of boys and girls in the family, the probability that the selected child is a girl is

Question

$\begin {array} {1 1} (1)\;\large\frac{1}{6} & \quad (2)\;\large\frac{1}{4} \\ (3)\;\large\frac{2}{3} & \quad (4)\;\large\frac{1}{2} \end {array}$