first to answer gets brainlyest and i will vote and thank you
when you exercise your muscles are hard at work.to allow your muculus to do all that work,they need to more nutrients and oxygen deliverd to them so they wil have the energy they need.which body systems supply them with those necessary things?

a)respiratory and skeletal
b)digestive and respiratory
c)circulatory and excretory
d)circulatory and respiratory