Answer:
It would be C.
(Circulatory)
Step-by-step explanation:
Breathing starts when you inhale air into your nose or mouth. It travels down the back of your throat and into your windpipe, which is divided into air passages called bronchial tubes. For your lungs to perform their best, these airways need to be open. Knowing that it all starts from the inside is what you should remember.
I hope this helps. :)