A radioactive sample S1 having an activity of $$5 \mu Ci$$ has twice the number of nuclei as another sample S2 which has anactivity of $$10 \mu Ci$$. The half lives of S1 and S2
can be

A

20 years and 5 years, respectively

B

20 years and 10 years, respectively

C

10 years each

D

5 years each