What Value Would Be Needed to Complete the Following Probability

Multiple Choice

What value would be needed to complete the following probability distribution?
$\begin{array}{|l|l|}\hline x & P(x) \\\hline 0 & 1 / 3 \\\hline 1 & 1 / 8 \\\hline 2 & 1 / 8 \\\hline 3 & 1 / 6 \\\hline 4 & \\\hline\end{array}$

A) $1 / 5$
B) $1 / 12$
C) $1 / 4$
D) $1 / 8$