If dy + z = d(y + z), which of the following must be true?  Select the correct option.
A) d = 0 and z = 0  B) d= 1 and y = 1  C) y = 1 and z = 0  D) d = 1 or y = 0  E) d = 1 or z = 0
dy + z = dy + dz   z = dz   case 1: z not= 0, d = z/z = 1   case 2: z = 0, 0 = d0 = 0   Combining 2 cases: d = 1 or z =0   E. is the answer.
<result>E</result>
If dy + z = d(y + z), which of the following must be true?