A student made the following observations about astronomical bodies. Observation 1: Mars reverses its direction of motion in the night's sky.
Observation 2: The stars move across the sky.

Which observation(s) can be explained using the heliocentric model but not the geocentric model?

(A)Only observation 1
(B) Only observation 2
(C) Both observation 1 and observation 2
(D) Neither observation 1 nor observation 2