The correct answer to this question is D, Right atrium → right ventricle → lungs → left atrium → left ventricle. In the heart, the atrium is the upper chamber where blood enters the heart. The right atrium is connected to the venous circulation, while the left atrium is connected to the lungs.
Ventricles are in the lower chamber of the heart. The right ventricle receives blood and pumps it into the lungs. The left ventricle pumps blood into the circulation system. Lungs are organs on the sides of the chest. They are filled with air and pass oxygen through the bloodstream.