(c)
The correct pattern shows closed magnetic field lines passing straight through the centre of the loop and looping around the outside, which matches the description in the textbook.
Source: Chapter 12, Section 12.2.3
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The textbook (Fig. 12.8) shows that field lines of a current-carrying circular loop form closed loops: they pass through the interior of the loop (appearing as straight lines at the centre) and curve around the outside. Examiners expect you to identify the option that shows this — closed, continuous field lines threading through the loop's centre, denser inside and spreading out symmetrically outside.