A particle starts from rest at $t=0$ and moves in a straight line with acceleration as shown in figure. The velocity of the particle at $t=3 \mathrm{s}$ is

• A

  $2 {\mathrm{m}\mathrm{s}}^{-1}$
• Correct answer
  B

  $4 {\mathrm{m}\mathrm{s}}^{-1}$
• C

  $6\mathrm{ }{\mathrm{m}\mathrm{s}}^{-1}$
• D

  $8\mathrm{ }{\mathrm{m}\mathrm{s}}^{-1}$

Hence, the correct answer is option: 'B'.