Pg 645 (577) - Q12
To get a product of 0, 0 must be one of the integers being multiplied.
0 times any of the 9 integers from 1 through 9 would be 0, so there are
9 ways to express 0 as a product of two different one-digit integers.
12, however, can only be expressed as 2*6
or 3*4, since the integers have to be one-digit. The answer
is therefore A.