What are the Newton's third law pairs in this diagram? In the diagram below, block $C$ accelerates downwards when released. I'm having some trouble identifying the third law (action $-$ reaction) force pairs in my free-body diagrams. Please provide any insights to determining the force pairs.

 A: *

*B and A - apply force on each other using friction (because they are sliding one over the other).
While it seems that B and C apply force on each other using the rope they are not count as third law because the force do not apply directly on each other - block C apply force on the rope (and vice versa so the rope and block C count as a third law pair) and then the rope apply force on block B (and vice versa so the rope and block  B count as a third law pair) .
The only remaining pair, A and C do not have any direct interaction between them and they are not applying any force on each other.
A: You can check that your pair is valid by reversing the words, e.g "A pulls on the rope" (the rope attached to A...) and "the rope pulls on A".  The pair should be forces of equal magnitude of opposite direction.  The pair of forces always act on different objects.
So zivs answer seems correct but you could add the above, and also add this:
"The earth pulls (down) on mass C" and "mass C pulls (up) on the earth", both are due to gravity.
