Which of the following ensures that blood does not flow backwards when the atria or ventricles contract?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Valves
The heart has valves between the atria and ventricles and at the openings of the large arteries. They open only one way, so blood moves forward when a chamber contracts and cannot flow back. The atria and ventricles are chambers that pump the blood; they do not stop it flowing back.