Final answer:
The option a) chordae tendineae are the tendons that hold the AV valve in place, preventing it from inverting into the atria during ventricular contraction.
Step-by-step explanation:
The tendons that hold the atrioventricular (AV) valve in place, preventing it from swinging upward into the atria, are called option a)chordae tendineae.
These tendinous cords are attached to the flaps of the AV valves and to the papillary muscles that extend from the ventricular surface. When the ventricles of the heart contract, the papillary muscles also contract, creating tension on the chordae tendineae and thereby holding the cusps of the atrioventricular valves in place, which prevents them from being forced into the atria during ventricular contraction and avoids regurgitation of the blood.