Question

A place where the horizontal component of Earth's magnetic field is zero lies at(A) geographic equator
(B) geomagnetic equator(C) one of the geographic poles
(D) one of the geomagnetic poles

Answer 1

The Earth is an oblate spheroid with geographic equator bulges at the equator.

There are basketball' shape comes from more combination of Earth's gravity and its rotation.

You can calculate the  equator 42.7 km larger than the diameter of the planet in the pole, There are equator is 40,075 km and 40,008 km at the poles.