Answer:
A
Step-by-step explanation:
The coaster wouldn’t eventually stop because there’s no fiction to stop it. In order for a object to stop, there must be a opposing force ( in this case, fiction).
It is true that the coaster could use hills to stop, but the coaster can’t use flat section to stop.
So what I think is that the answer is A.
Fun Fact:
It would be really tough just to stand up without friction.
I hope this help and have a nice day :)