The positive integers x, y and z are such that x is a factor of y and y is a factor of z. Is z even.

1) xz is even
2) y is even.



Question 'Is z even?' --> 'Does the prime box for Z contain the number 2?'



(2) is the easy statement. If y is even, then y has a 2 in its prime factorization. But if y is a factor of z, then all the prime factors of y are also in z. Therefore, z contains a '2' in its prime box, so Z is even. Sufficient.

(1) means that either x is even, z is even, or both.
* If z is even, then the answer to the question is an immediate Yes.
* If x is even, then x contains a '2' in its prime factorization. Since x is a factor of y, so does y. Since y is a factor of z, so does z. So z is even. Sufficient.

Either is sufficient, so, D.