If py + z = p(y + z), which of the following must be true?
Choose the correct choice from the following options:	A) x = 0 and z = 0	B) p = 1 and y = 1	C) p = 1 and z = 0	D) p = 1 or y = 0	E) p = 1 or z = 0
py + z = py + pz   z = pz   case 1: z not= 0, p = z/z = 1   case 2: z = 0, 0 = p0 = 0   Combining 2 cases: p = 1 or z =0   E. is the answer.
<result>E</result>
If py + z = p(y + z), which of the following must be true?