A S.H.M. has amplitude ‘a’ and  time period T. The maximum velocity will be

• A

  $\frac{4\mathrm{a}}{\mathrm{T}}$

• B

  $\frac{2\mathrm{a}}{\mathrm{T}}$

• C

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{a}}{\mathrm{T}}}$

• D

  $\frac{2\mathrm{\pi a}}{\mathrm{T}}$