1. $a, b$ are positive integer divisors of 1995, then the number of ordered pairs $(a, b)$ is ().
(A) 16
(B) 32
(C) 64
(D) 256
1. D $1995=3 \cdot 5 \cdot 7 \cdot 19$, the number of positive divisors is 24 $=16$. For the pair $(a, b)$, $a$ has 16 possible values, and for each $a$, $b$ also has 16 possible values. Therefore, the number of pairs $(a, b)$ is $16 \times 16=256$ (pairs).