If We Observe One Edge of a Planet to Be

Multiple Choice

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

A) The planet is actually two bodies, one moving toward us, the other away from us.
B) The planet is rotating.
C) The planet is in the process of formation.
D) The planet is in the process of falling apart.