If (1+z)y=y, which of the following must be true? Pick:
A) z=-1 or y=0	B) z=0 or y=-1	C) z=1 or y=1	D) z=-1 or y=-1	E) z=0 or y=0
We have (1+z)y=y.   If x=0, y=y. True   If y=0, (1+z)*0=0 True   So, z=0 or y=0 will be the answer.
<result>E</result>
If (1+z)y=y, which of the following must be true?