The oscillating electric and magnetic field vectors of electromagnetic wave are oriented along(a) The same direction and in phase(b)The same direction but have a phase difference of 90°(c)Mutually perpendicular directions and are in phase(d)Mutually perpendicular directions but has a phase difference of 90°

(c)

The direction of oscillations of E and B fields are perpendicular to each other as well as to the direction of propagation. So, electromagnetic waves are transverse in nature.

The electric and magnetic field oscillate in same phase.

Though in free space the E and B vector are perpendicular to each other and in phase .this may not always be the case and depends on the medium,and the source of fields.

For this question ,as no other information is given the answer is (C)