Which one of these motions is at constant acceleration?

[Lilygu3]

Homework Statement

Which one of these motions is at constant acceleration?
A) A car moving at a constant speed and constant direction.
B) A train making stops along its route.
C) A moon orbiting a planet.

Homework Equations

The Attempt at a Solution

I believe that A is an acceptable answer, since the car is at a constant acceleration of zero.
My teacher says C is the only correct answer.

Thank you for your input!

 

[SteamKing]

Your teacher needs to go back to school.

 

[rude man]

I agree. The teacher seems to be entertaining the notion that the orbit of the moon is a perfect circle, which it ain't.

 

[Daeho Ro]

How the teacher can select C? Have you asked what is the reason?