Answer the following question given this paragraph: 

Coronary heart disease often does not have any symptoms. A symptom of coronary heart disease is chest pain. Occasional chest pain can happen during times of stress or physical activity. The pain of angina means the heart muscle fibers need more oxygen than they are getting. Most people with coronary heart disease often have no symptoms for many years until they have a heart attack.


Q: The pain of angina means the heart muscle fibers need more what?

 Choices:

- water

- carbon

- nitrogen

- oxygen

A:
oxygen
