The Fact That $\mathbf { r } ( t ) \times \mathbf { v } ( t )$

Multiple Choice

The fact that $\mathbf { r } ( t ) \times \mathbf { v } ( t )$ is constant implies that

A) The speed of a planet around the sun is a constant.
B) The motion of the planet lies in a plane.
C) The speed of the sun is a constant.
D) The force between the planet and the sun is a constant.
E) The position of the planet is unrelated to the sun.