A runner is three quarters of the way through a marathon. Which systems are working to maintain oxygen levels for the runner's muscles?
Aintegumentary, excretory, nervous, endocrine
Bcirculatory, excretory, nervous, endocrine
Crespiratory, excretory, nervous, endocrine
Dcirculatory, respiratory, nervous, endocrine
Aintegumentary, excretory, nervous, endocrine
Bcirculatory, excretory, nervous, endocrine
Crespiratory, excretory, nervous, endocrine
Dcirculatory, respiratory, nervous, endocrine