Answer is A.
The angle that the lines of force make with the Earth's surface at any given place is called the Angle of Dip and varies from 0 degrees at the magnetic equator, to virtually 90 degrees at the magnetic poles.
The lines of force around the magnetic equator of the Earth are perfectly horizontal. So the magnetic needle will become horizontal there. Thus, the angle of dip at the magnetic equator of the Earth will be 0 degrees.