3. How many squares have 7 as their units digit?
A 0
B 1
C 2
D 3
E 4
3. A Consider the units digits of the squares of the integers $0,1,2,3, \ldots, 9$. These are $0,1,4,9,6,5,6,9,4,1$. Note that none of these is 7 , so no square ends in a 7 .