From (1) xy > 0 means both have same sign, hence if both are negative:
then xyz < 0 if z < 0, and xyz > 0 if z is positive
And if both are poitive, then xyz is always > 0. So (1) is not enough.
From (2) xz > 0, so here too both x and z have same sign, and hence y will also have same sign
But if x,y and z are negative, then xyz < 0 and if x,y and z are positive, then xyz > 0
From(1) and (2), x, y,z can be either all +ve or all -ve, so the answer is E.
Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)