Two charges $+q$ and $-q$ are placed at a distance $a$ in a uniform electric field. The dipole moment of the combination is $2qa(\cos \theta \hat{i} + \sin \theta \hat{j})$, where $\theta$ is the angle between the direction of the field and the line joining the two charges. Which of the following statement$(s)$ is/are correct?

• A
  The torque exerted by the field on the dipole vanishes
• B
  The net force on the dipole vanishes
• C
  The torque is independent of the choice of coordinates
• D
  The net force is independent of $a$