A current carrying square loop is placed near an infinitely long current carrying wire as shown in figure. The torque acting on the loop is:

Zero

The correct answer is Option (4) → Zero

Torque acting on loop, $\vec{\tau}=\vec{M} \times \vec{B}$, where $\vec{M}$ is the magnetic moment and $\vec{B}$ is the external magnetic field.

$|\tau|=M B \sin \theta$

Since $\theta=0^{\circ} \Rightarrow \tau=0$, where $\theta$ is the angle between the magnetic moment and external magnetic field.