If Sample Points A, B, C, and D Are the Only

If sample points A, B, C, and D are the only possible outcomes of an experiment, find the probability of D using the table below.
$\begin{array}{l|cccc}\text { Sample Point } & A & B & C & D \\\hline \text { Probability } & 1 / 7 & 1 / 7 & 1 / 7 &\end{array}$

A) $\frac { 1 } { 4 }$

B) $\frac { 4 } { 7 }$

C) $\frac { 1 } { 7 }$

D) $\frac { 3 } { 7 }$