9. A store has 10 televisions, arranged in a row. It is known that 3 of them are defective. If we conduct a random inspection of these televisions, what is the probability that all the defective ones appear in the first 5 televisions?
(A) $\frac{3}{10}$
(B) $\frac{1}{12}$.
(C) $\frac{2}{7}$.
(D) $\frac{1}{7}$.
(E) None of the above.
9.3 defective items placed on 10 positions is ( $\left.\begin{array}{c}10 \\ 3\end{array}\right)$, and all 3 defective items placed in the first 5 positions is ( $\left.\begin{array}{l}5 \\ 3\end{array}\right)$, so the probability that all defective items appear in the first 5 televisions is ( ( $\left.\begin{array}{l}5 \\ 3\end{array}\right) /\binom{10}{3}$ $=1 / 12$. Therefore, the answer is (1).