If $10 \%$ of $s$ is $t$, then $s$ equals
(A) $0.1 t$
(B) $0.9 t$
(C) $9 t$
(D) $10 t$
(E) $90 t$
The percentage $10 \%$ is equivalent to the fraction $\frac{1}{10}$.

Therefore, $t=\frac{1}{10} s$, or $s=10 t$.

ANswer: (D)