Earth's magnetic field always has horizontal component except at

Solution:

The Earth's magnetic field lines are perpendicular to the Earth's surface at the magnetic poles. This means that at the magnetic poles, the entire magnetic field is directed vertically (either upwards or downwards). Consequently, the horizontal component of the Earth's magnetic field is zero at the magnetic poles. At the magnetic equator, the magnetic field lines are parallel to the Earth's surface, so the horizontal component is maximum and the vertical component is zero.