Answer the following question given this paragraph: 

"Cardio" has become slang for aerobic exercise that raises your heart rate for an extended amount of time. Cardio can include biking, running, or swimming. Can you guess one of the main organs of the cardiovascular system? Yes, your heart.


Q: "cardio" has become slang for what type of exercise that raises your heart rate for an extended amount of time?


A:
aerobic