If You See a Bright "Star" in the Sky, How

If you see a bright "star" in the sky, how could you tell whether it is a star or a planet?

A) Planets are too dim to be seen without a telescope.
B) Planets are round; stars have five points.
C) Planets always appear right next to the Moon.
D) Look at it several days later-if it's a planet, it will move across the background stars.