Newbie question Find all related objects to related object??

Hello everyone, I 'm new to Django only started two weeks ago ,
I’m working on simple Api using views functions :
I have these models:
class A

class B

class C

a is instance of A
how I can return (all Cs that are related to a) in my view function

Referencing a ForeignKey in reverse is very similar to accessing either side of a ManyToMany relationship - and that’s where it’s documented.
Also see Making queries | Django documentation | Django