An investigator has \(0.010 \mu \mathrm{g}\) samples of two isotopes of strontium, \({ }^{89} \mathrm{Sr}\left(t_{1 / 2}=51\right.\) days \()\) and \({ }^{90} \mathrm{Sr}\left(t_{1 / 2}=28\right.\) years \()\). The samples contain approximately the same number of atoms. What can you say about the activity of the two samples?

A. The \({ }^{89} \mathrm{Sr}\) sample has a higher activity.

B. The \({ }^{90} \mathrm{Sr}\) sample has a higher activity.

C. The two samples have about the same activity.