Here, given that a circular coil expands radially in a region of magnetic field and no electromotive force (e.m.f.) is produced in the coil which means e=0 as we know that

where B is the magnetic field strength, l is the length and v is the velocity of loop.

Also circular coil expands radially means magnetic field is perpendicular to the plane of circular coil but e=0 which means magnetic field should be in the plane of circular coil so that its component which perpendicular to plane of coil is zero. Hence option (b) is correct. Now if the magnitude of magnetic field decreases with the magnetic flux then also . So option (c) is also correct now for rests options i.e. option (a) has no meaning for electromotive force to be zero as this equation still valid so option (a) is wrong also option (d) saying same thing only taking component but we discussed that magnitude should also decease hence (d) is also wrong.

Therefore, options (b) & (c) are the correct.