1.17 If $y z: z x: x y=1: 2: 3$, then $\frac{x}{y z}: \frac{y}{z x}$ equals
(A) $3: 2$.
(B) $1: 2$.
(C) 1:4.
(D) $2: 1$.
(E) $4: 1$.
(23rd American High School Mathematics Examination, 1972)
[Solution] Since it is known that $y z: z x=1: 2$, therefore $2 y z=z x$, then
$$
\frac{z x}{y z}=2, \quad \frac{y z}{z x}=\frac{1}{2} \text {. }
$$

So the ratio $\frac{x}{y z}: \frac{y}{z x}=\frac{z x}{y z}: \frac{y z}{z x}=2: \frac{1}{2}=4: 1$. Therefore, the answer is $(E)$.