The result of adding a number to itself is usually unequal to the result of multiplying the number by itself. For how many different numbers are these results equal?
A none
B. one
C. two
D. four
0 + 0 = 0
0 * 0 = 0
1 + 1 = 2
1 * 1 = 1
etc.
http://en.wikipedia.org/wiki/Number