The velocity vector of the motion described by the position vector of a particle $r=2t\hat{\mathbf{i}}+t^2\hat{\mathbf{j}}$ is given by         

• A

  $v = 2\hat{\mathbf{i}}+2t\hat{\mathbf{j}}$

• B

  $v = 2t \hat{\mathbf{i}}+2t \hat{\mathbf{j}}$

• C

  $v = t \hat{\mathbf{i}}+t^2 \hat{\mathbf{j}}$

• D

  $v = 2 \hat{\mathbf{i}}+t^2 \hat{\mathbf{j}}$