JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Electromagnetic Induction

Magnetic flux is $\Phi =BA\cos \theta$, where $\theta$ is the angle between $\vec{B}$ and the coil's normal (initially $\theta =0$, $\Phi =BA$). Flux depends on exactly three quantities, so it changes if (A) the field magnitude $B$ changes, (B) the enclosed area $A$ changes, or (C) the orientation angle between field and coil plane changes. A, B and C each alter $\Phi$. Statement D (abruptly reversing the field at fixed magnitude) only reverses the sign of an already-maximum flux and is a special case of an orientation change, not an independent mechanism. The three fundamental ways are A, B and C, so the answer is 'A, B and C only'.