矢量 $\boldsymbol{a}$ 的物质体积分的随体导数等于

1. A

   $\int_\tau \left(\frac{d\boldsymbol{a}}{dt}+\boldsymbol{a}\operatorname{div}\boldsymbol{v}\right)d\tau$

   正确
2. B

   $\int_\tau \frac{\partial\boldsymbol{a}}{\partial t}\,d\tau$

3. C

   $\int_\tau \frac{d\boldsymbol{a}}{dt}\,d\tau$

4. D

   $\int_\tau \left(\frac{\partial\boldsymbol{a}}{\partial t}-\boldsymbol{a}\operatorname{div}\boldsymbol{v}\right)d\tau$