6. (27th American High School Mathematics Examination) Let there be an $n$-term geometric sequence, with the first term being 1, the common ratio being $r$, and the sum being $s$, where $r$ and $s$ are non-zero numbers. Then the sum of the new geometric sequence obtained by replacing each term of the original sequence with its reciprocal is
A. $\frac{1}{s}$
B. $\frac{1}{r^{n} s}$
C. $\frac{s}{r^{n-1}}$
D. $\frac{r^{n}}{s}$
6. Choose C.

Slightly explained: The sum of the terms in the new sequence is $1+\frac{1}{r}+\cdots+\frac{1}{r^{n-1}}=\frac{r^{n-1}+r^{n}+\cdots+1}{r^{n-1}}=\frac{s}{r^{n-1}}$.