6・3 If $a=(-3)^{-4}, b=-3^{4}, c=-3^{-4}$, then the incorrect conclusion among the following is
(A) $\log _{3} a=-4$.
(B) $\lg b c=0$.
(C) $a, c$ are opposite numbers.
(D) $a, b$ are reciprocals.
(China Sichuan Province Junior High School Mathematics League, 1989)
[Solution] Given $a=(-3)^{-4}=\frac{1}{(-3)^{4}}=\frac{1}{3^{4}}>0$,
and
$$
c=-3^{-4}=-\frac{1}{3^{4}}<0,
$$

then $a, c$ are opposite numbers, and $\log _{3} a=-4, \lg b c=\lg 1=0$. Therefore, the answer is $(D)$.