If $(p q)(q r)(r p)=16$, then a possible value for $p q r$ is
(A) 0
(B) 2
(C) 4
(D) 8
(E) 16
Since $(p q)(q r)(r p)=16$, then $p q q r r p=16$ or $p p q q r r=16$ which gives $p^{2} q^{2} r^{2}=16$.

Thus, $(p q r)^{2}=16$ and so $p q r= \pm 4$.

Using the given answers, $p q r$ is positive and so $p q r=4$.

ANswer: (C)