A force-time graph for a linear motion is shown in figure where the segments are circular. The linear momentum gained between zero and 8 second is

• A

  $-2\mathrm{\pi }\mathrm{newton}\times \mathrm{second}$

• B

  $\mathrm{Zero}\mathrm{newton}\times \mathrm{second}$

• C

  $+4\mathrm{\pi }\mathrm{newton}\times \mathrm{second}$

• D

  $-6\mathrm{\pi }\mathrm{newton}\times \mathrm{second}$