Why Are Venus and Mercury Often Called "Morning Star" and "Evening

Multiple Choice

Why are Venus and Mercury often called "morning star" and "evening star"?

A) They look more like stars than the other planets do.
B) They both rotate quite slowly and have long mornings and evenings.
C) They are both reddish in colour, like the Sun near the horizon.
D) They are only visible just before sunrise or just after sunset.