AMC8 1986 Problem 12

The table to the right displays the grade distribution of the 30 students in a mathematics class on the last two tests. For example, exactly one student received a ‘D’ on Test 1 and a ‘C’ on Test 2 (see circled entry). What percent of the students received

\begin{array}{|c|c|c|c|c|c|} \hline S & & B & C & D & F \\ \hline A & 2 & 2 & 1 & 0 & 0 \\ \hline B & 1 & 4 & 3 & 0 & 0 \\ \hline C & 1 & 3 & 5 & 2 & 0 \\ \hline D & 0 & 0 & (1) & 1 & 1 \\ \hline F & 0 & 0 & 2 & \mathbf{1} & 0 \\ \hline \end{array}

the same grade on both tests?

Answer Choices
A. 12 \%
B. 25 \%
C. 33 \dfrac{1}{3} \%
D. 40 \%
E. 50 \%