Astudent made the following observations about astronomical bodies. observation 1: mars reverses its direction of motion in the sky. observation 2: the stars appear brighter at different times of the year. which observation(s) can be explained using the heliocentric model? a. only observation 1 b. only observation 2 c. both observation 1 and observation 2 d. neither observation 1 nor observation 2

If we compare and contrast electromagnetic waves with sound waves, all but one statement is true. that is a) sound waves require a medium to travel while electromagnetic waves do not. b) electromagnetic waves can travel through the vacuum of space while sound waves cannot. c) electromagnetic waves must have a medium in which to travel, but sound waves can travel anywhere. eliminate d) sound waves must bounce off of matter in order to travel while electromagnetic waves do not require matter to be present.