The moon orbits the earth once in about a. 365 days b. 28 days c. 24 hours d. 7 days

Option B. 28 days

Explanation:

The moon orbits the Earth in about 28 days.

Moon also takes 28 days to rotate once on its own, that is why it seems still in it's position.  

The moon rotates around the Earth in an elliptical orbit. The moon rotates in slower rate when it is closest to earth and rotates in faster rate when far from earth. The side of moon facing earth surface is called the near side. During new moon phase, when the moon comes between the Earth and the sun, the back side of the moon gets hide by daylight.

The moon changes its shape during rotation of earth as per the lunar theory. It involves several phases in the given sequence First Quarter following Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent, New Moon and Waxing Crescent and repeats.

Hence, the correct option is B. 28 days.