If xyz > 0, is x*y^2*z^3 < 0?
1) y <0> 0
I loath DS but that's why I decided to give this a shot:
original stem: xyz > 0 means all are positive or 2 out of the three are negative.
(1) y is negative. Tells me that either x or z is negative. if that's the case, then x*y^2*z^3 would have to be negative since y^2 removes one of the negatives from the equation. Sufficient.
(2) x is positive. Doesn't give much as y and z could both be positive or both be negative. if y and z are negative, the answer is "yes" but if y and z are positive, then the answer is "no". not sufficient.
my choice: A