Data Sufficiency

(x^4)(y^3)(z^7)<0, xyz<0?

1.y<0
2.z>0


oa E

For this kind of question try to find example/counter-example.

(x^4)(y^3)(z^7)<0, xyz<0?

1.y<0
All respect: (x^4)(y^3)(z^7)<0
y<0 then z>0 given x^4 is positive and we have to do (x^4)(y^3)(z^7)<0
If y=-1, z=1, x=1 then xyz<0
If y=-1, z=1, x=-1, then xyz>0
Insufficient

2.z>0
All respect: (x^4)(y^3)(z^7)<0
z>0 then y<0
We have the same conditions as for 1) (z>0 and y<0)
so it is also insufficient

1and 2 gives you y<0 and z>0 so it is exactly the same.... and insufficient

The solution can be generalized as:

1. y<0
For the given condition to be true z>0 but x<0 or x>0.
If x<0 then xyz>0
else if x>0 then xyz<0

2. z>0
Implies y<0 from the given condition.
Again x<0 or x>0.
Which again gives xyz>0 or xyz<0

3. Combining the 2 cases doesn't help as x<0 or x>0

So answer is E.