The moon orbits

a. Earth.

c. Saturn.

b. the sun.

d. Mercury.

No offence but why is this even a question

A. Earth

Of course, the answer is "Earth". We often see a bright celestial body at night, which is called "The Moon". So, obviously, the Moon orbits the Earth.

Planet Saturn also has moons, Mercury hasn't and Sun has planets, comets etc. NOT moons which orbit it.