7. How many two-digit squares have the property that the product of their digits is also a square?
A 0
B 1
C 2
D 3
E 4
7. B The two-digit squares are $16,25,36,49,64,81$. The products of their digits are $6,10,18,36,24,8$, respectively. So exactly one two-digit square has the required property, namely 49 .