The activity of a radioactive sample decreases to one tenth of the original activity $$A_{0\ }$$ in a period of one year. After 9 more years its activity would be

A

$$\frac{A_{0\ }}{100}$$

B

$$\frac{A_{0\ }}{90}$$

C

$$\frac{A_{0\ }}{10^{10}}$$

D

$$\frac{A_{0\ }}{10^{9}}$$