1) B
Largest to smallest: universe, galaxy, solar system, planet
2) I would say C. It makes the most sense as it's larger than the average, and the other options are too small.
3) B
The sun is larger than Earth, so it'd be point C.
The moon is smaller than Earth, so it'd be point A.
The milky way galaxy is larger than our solar system (we're part of the milky way), so it'd be the farthest point (point D).
Point B is located between point A and point C, so it's perfect!