An electric dipol
The field due a point charge is always radial (radially outwards for positive charge and radially inwards for negative charge). A dipole placed in that electric field will never feel equal and opposite forces due to the radial nature of the field. Therefore, option (a) and (b) are incorrect.
Torque on the dipole may be zero in the case when the dipole is placed along the electric field (as in that only case, and will be parallel or antiparallel, thus torque will be zero.)
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