Correct answer is B.
$\begin{array}{l}
\mathrm{T}=2 \pi \sqrt{\frac{\mathrm{m}}{\mathrm{k}}} \\
\mathrm{T}_{1}=\mathrm{T} \\
\mathrm{m}_{1}=1 \mathrm{~kg} \\
\mathrm{~m}_{2}=4 \mathrm{~kg} \\
\mathrm{~T}=2 \pi \sqrt{\frac{1}{\mathrm{k}}} \\
\mathrm{T}_{2}=2 \pi \sqrt{\frac{4}{\mathrm{k}}} \\
\mathrm{T}_{2}=2 \mathrm{~T}
\end{array}$