Q$6.$ Select the correct statement. Theoretically, we can know the shape of the Earth by measuring

distances X and Y on the surface of the Earth: X is the distance corresponding to $1$ degree measured

from the pole, while Y is the one from the equator. It turned out that

A$.$ X and Y are both difficult to measure due to the mountains.

B$.$ X$=$Y$,$ indicating a perfect sphere.

C$.$ X Y$,$ indicating an elongated shape along the perpendicular direction to the rotation axis of

the Earth.Q$6.$ Centrifugal force: force outward the center