Oxygen rich blood returns from the lungs to the heart. Which 2 systems are most directly involved in this process. Respiratory and circulatory
Excretory and digestive
Circulatory and excretory
Digestive and respiratory

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the answer to you question is   jet streams

the cell cycle is the final answer! : )

the ems is the abbreviation for the emergency medical services. it is a service provided by a group of medical professionals specialised doctors and other healthcare staff.

any one can call 911 in case of any medical emergency and a group of health care professional will come and give the treatment required. every day the ems staff receive many phone call, which are related to different types of medical emergencies, out of which 25-28% are exclusively related to the respiratory issues.

so, the correct answer is 25-28%.