1. Given that $a$, $b$, and $c$ are all positive numbers not equal to 1, and $a^{-2}=b^{3}=c^{6}$. Then the value of $a b c$ is ( ).
(A) 3
(B) 2
(C) 1
(D) $\frac{1}{2}$
-1.C.
From $a^{-2}=b^{3}=c^{6}$, we get $a=c^{-3}, b=c^{2}$.
Then $a b c=c^{-3} c^{2} c=1$.