Question

Parallax of the stars is created by
A. different phases of the moon
B. different locations of Earth in its orbit
C. motion of the stars

Answer 1

b

Answer 2

it can be both B and C..., but probably you want B: Parallax (the apparent shift relative to the background stars) can be measured when the earth moves from one side of its orbit to the other (6 months) This change in angle is used to measure the distances to stars

Answer 3

But stars don't move!

Well, actually they do, but slowly compared to the motion of earth.
So you're right, but for homework they usually want b as the answer.

Answer 4

To get the true space motion of a star we measure its radial speed by looking at the Doppler shift in their spectra, and get the tangential speed by looking at their shift relative to the background stars (parallax)