+1 for C. To find the answer to this question, we need to know a) if any of x,y,or z is equal to zero or not. b) yz > 0 or not. (xy)^2*(yz).

Statement 1 gives yz>0 and y,z are not equal to 0. --> Not sufficient

Statement 2 gives x and z are not equal to 0. --> Not sufficient

Both 1 and 2 ---> Sufficient. We come to know that x,y,and z are non zero and that yz>0. Hence option C.

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