Bunuel wrote:

Is wz(x + y) a negative even integer?

(1) w, x, and y are positive odd integers.

(2) z is a negative even integer.

(1) If x and y are positive odd integers, then their sum will be a positive even integer. That multiplied by w, which is another positive odd integer, will also result in a positive even integer. So w*(x+y) is a positive even integer. But we dont know about z. z could be a positive or negative integer, even or odd integer, or it could be in decimals also. So we cannot determine whether w*z*(x+y) will be a negative even integer or not. Not sufficient.

(2) z is negative even, but nothing mentioned about others. So not sufficient.

Combining, w*(x+y) is positive even integer, and that multiplied by z, which is a negative even integer, will result in a negative even integer only. Sufficient.

Hence

C answer.