13. D.
$$
P=\frac{\mathrm{C}_{5}^{1}}{\mathrm{C}_{6}^{2}}=\frac{5}{\frac{6 \times 5}{2}}=\frac{1}{3}
$$
13. Two different numbers are randomly selected from the set $\{-2,-1,0,3,4,5\}$ and multiplied. The probability that the product is 0 is ( ).
(A) $\frac{1}{6}$
(B) $\frac{1}{5}$
(C) $\frac{1}{4}$
(D) $\frac{1}{3}$
(E) $\frac{1}{2}$