An electric dipole is placed in a non-uniform electric field, such that the dipole moment is parallel to the electric field. The dipole will experience

a force only

The correct answer is Option (4) → a force only

Force on an electric dipole in a non-uniform electric field:

$\vec{F} = (\vec{p} \cdot \nabla) \vec{E}$

If dipole moment $\vec{p}$ is parallel to the electric field $\vec{E}$, the dipole experiences a net force in the direction of increasing field strength. No torque acts because $\vec{p} \parallel \vec{E}$.

The dipole will experience a net force along the direction of the electric field.