The Final (Stable) Orientation of an Electric Dipole in a E-Field

The final (stable) orientation of an electric dipole in a E-field occurs when the torque $\tau$ on the dipole and the potential energy U of the dipole are arranged as follows:

A) $\tau$ is a maximum and U is a minimum.
B) $\tau$ is a minimum and U is zero.
C) $\tau$ is zero and U is a minimum.
D) $\tau$ is zero and U is zero.