IIT-JEE 2011 · Paper 2, Physics question 25

Magnetic field lines never begin or end ($\nabla\cdot\vec B=0$), which rules out the radial patterns (A) and (B); those are fields of point charges.

Closed circular loops (C) describe the magnetic field around a straight current. They also describe the induced electric field around a changing magnetic flux ($\oint\vec E\cdot d\vec l=-\frac{d\Phi_B}{dt}$), so (C) is valid for both.

(D) is the field of a magnetic dipole, with lines that close through the source. An electric field cannot have this pattern.

(C)