Two pure samples of radioactive nuclides X and Y have the same initial number of atoms. The half-life of X is ${T_{\frac{1}{2}}}$.

After a time equal to 4 half-lives of X the ratio $\frac{{{\text{number of atoms of X}}}}{{{\text{number of atoms of Y}}}}$ is $\frac{1}{8}$.

What is the half-life of Y?

A.     $0.25{T_{\frac{1}{2}}}$

B.     $0.5{T_{\frac{1}{2}}}$

C.     $3{T_{\frac{1}{2}}}$

D.     $4{T_{\frac{1}{2}}}$

D