The power radiated per unit solid angle for an oscillating electric dipole is proportional to , where is the angle between the electric dipole moment and point where the radiation is being measured. This implies that the radiated power per unit solid is along the axis and maximum on the  plane. This implies that it is answer (A) or (C) that is correct. To determine whether the electric field is the plane or in the direction, recall that the electric field in the radiation zone of an oscillating electric dipole is in the direction which in this case is in the  plane. Therefore, answer (C) is correct.
