The torque equals the vector (cross) product of the electric dipole moment and the external electric field.
Therefore, it must be perpendicular to the electric dipole moment
(thus it can't be into the screen or out of the screen).
Also, it must be perpendicular to the external electric field
(thus it can't be right or left).
Using the right-hand rule, your extended right thumb points
toward the bottom of the screen.
Click here to return.