B. ventricles
The chordae tendinae, also referred to as heart strings, are tendons that connect the atrioventricular (tricuspid) valves to the muscular wall of the heart. These chords are made predominantly of collagen, while the remaining part is elastin. They play the vital role of maintaining the structure of the valves they connect to. Due to the high pressure generated within the heart, it is entirely possible for the atrioventricular valves to turn inside out. The chordae tendinae prevent this from happening and keep the valves functioning properly.