9. The sum of the prime factors of the arithmetic square root of the largest perfect square that divides 12! is ( ).
(A) 5
(B) 7
(C) 8
(D) 10
(E) 12
9. D.

Notice that, $12!=2^{10} \times 3^{5} \times 5^{2} \times 7 \times 11$.
Then the largest perfect square that can divide 12! has the square root of $2^{5} \times 3^{2} \times 5$.
Therefore, the sum of the prime factors is $2+3+5=10$.