An astronomer is studying two stars that are the same distance from Earth. Star X appears brighter than star Y. Which statement best explains this observation?
A: Star X is larger than star Y.

A large, solid spherical body in the solar system is classified as a moon. Which characteristic of the body gives it this classification?
A: It orbits a nearby planet.

Which physical characteristic of Earth is similar to a physical characteristic of the Moon?
A: its mountain ranges

Inside cells, special molecules carry messages from the membrane to the nucleus. Which body system uses a similar process?
A:
endocrine system