- Brent@GMATPrepNow
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Answer is III only.. i.e. C
According to the original equation: either x or z is less than 0 but not both. About y we dont know if it is less than or greater than 0. Because its exponent is even, it is not changing the sign of the equation. So we can't be sure about y
but xz has to be definitely less than 0 because either x or z is less than 0

