If ab - c = a(b - c), which of the following must be true?	Choose one.
A) a=0 and c=0 B) a=1/2 and b=2 C) b=1 and c=0 D) a=1 or c=0 E) a=1/2 or c=0
ab-c = a (b-c)   ab - c = ab - ac   c= ac   ac-c = 0   c(a-1) = 0   Either c = 0; or a = 1   a=1 or c=0 is the answer
<result>D</result>
If ab - c = a(b - c), which of the following must be true?