Answer:
Given:
x is a factor of y --> , for some non-zero integer ;
y is a factor of z --> , for some non-zero integer ;
So, .
Question: is z even? Note that will be even if either or is even
(1) even --> either even, so the answer is directly YES or is even (or both). But if is even and as then z must be even too (one of the multiples of z is even, so z is even too). Sufficient.
(2) even --> as then as one of the multiples of z even --> z even. Sufficient.
Answer: D.
