The correct pattern of magnetic field lines of the field produced by a current carrying circular loop is :

Hint

Use the right-hand thumb rule to determine the direction of the magnetic field lines.

Quick oral answer

The magnetic field lines of a current-carrying circular loop are concentric circles around the loop. The direction of the field lines can be determined using the right-hand thumb rule. When the thumb points in the direction of the current, the fingers will wrap around the loop in the direction of the field lines. Therefore, the correct pattern of magnetic field lines is shown in option (d).