Given that yz is positive, if xyz (x times yz) is negative, x must be negative. y and z, however, are not as clear. Either both are positive or both are negative.

Neither (A) nor (B) is correct because while x is negative, y and z could be either positive or negative. If y or z is positive, the product is negative.

(C) must be positive. x^2 is always positive and yz is positive, so the product of the two, (x^2)yz, is positive as well.

(D) need not be positive. x is negative and y^2 must be positive regardless of the sign of y. If z is negative, the result is positive, but if z is positive, the result is negative. The same logic applies to (E), only y and z are reverse. (C) is the correct choice.