If wy + z = w(y + z), which of the following must be true?	Pick.
A) x = 0 and z = 0 B) w = 1 and y = 1 C) w = 1 and z = 0 D) w = 1 or y = 0 E) w = 1 or z = 0
wy + z = wy + wz   z = wz   case 1: z not= 0, w = z/z = 1   case 2: z = 0, 0 = w0 = 0   Combining 2 cases: w = 1 or z =0   E. is the answer.
<result>E</result>
If wy + z = w(y + z), which of the following must be true?