Answer:
The correct answer is - prevents the prolapse and hold them in the closed position so prevent from backflow of blood into atria.
Explanation:
The chordae tendineae also known as the heartstrings which are attached to the ventricular side of the bi capsid and tricuspid valve flaps. These are attached to the papillary muscles of the valves in the heart.
Blood flows to the ventricles from atria down the pressure gradient during systole. Heartstrings are relaxed due to the AV valves are forced open but during ventricular systole, these tendineae prevents backflow of the blood that in atria as they are tensed and prevent them to prolapse.
Thus, the correct answer is - prevents the prolapse and hold them in the closed position so prevent from backflow of blood into atria.