Conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An emf will be induced only when the magnetic flux changes. If there is no change in magnetic flux, then induced emf will be zero. An emf will be induced in the loop only when

i. The loop is rotated about a diameter

ii. Deforming the loop.

If the loop is deformed, the area of the loop inside the magnetic field changes. So magnetic flux will change leads to induce an emf. On rotating about its axis, the magnetic flux does not change. So an emf induced in the loop is zero.

Thus, Option C and D are correct.