How to get a collection of related elements to a collection of parent objects?

Question

Laravel

Good afternoon!
How to get a collection of related elements to a sorted collection of parent objects?
For example,
A -> hasMany (B) -> hasOne(C)
Initial data: an instance of class A.
I get a collection B for element A: A->B()
I want to get: a collection of C elements for all B bound to A, preferably in 1-2 lines, without going through the foreach loop on B.