If a simple harmonic motion is represented by $\frac{{\mathrm{d}}^2\mathrm{x}}{{\mathrm{dt}}^2}+\mathrm{\alpha x}=0;$its time period is :

• A

  $2\mathrm{\pi \alpha }$

• B

  $2\mathrm{\pi }\sqrt{\mathrm{\alpha }}$

• C

  $\frac{2\mathrm{\pi }}{\mathrm{\alpha }}$

• D

  $\frac{2\mathrm{\pi }}{\sqrt{\mathrm{\alpha }}}$