Final answer:
The part of the cardiac cycle in which the cardiac muscle obtains its oxygen and gets rid of waste products is diastole.
Step-by-step explanation:
The part of the cardiac cycle in which the cardiac muscle obtains its oxygen and gets rid of waste products is diastole. During diastole, the heart chambers relax and fill with blood. This allows oxygen to be delivered to the cardiac muscle, which needs a constant supply of oxygen to function properly. Diastole also allows waste products, such as carbon dioxide, to be removed from the muscle. So, the correct answer is Diastole (option B).