The atrioventricular (av) valves of the human heart have "heart strings" attached to the ventricular side of the valve flaps. these strings, properly called chordae tendinae, reach downward from the underside of the valves and attach to the bottom of the ventricles. they are long enough to just allow the valve flaps to shut. what probably the biological role of the chordae tendinae?

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.

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.

the two answers are a, the population of birds with large beaks will increase on the island, and c, the trait for large beaks will be passed on to future generations through natural selection. the reason for that is because if the birds that have beaks developed for eating small seeds lose all of their food, they will go hungry and eventually starve because they physically cannot eat the large seeds, therefore making the population of large beaked birds higher. also, if the trait of large beaks are dominant on the island over small beaks, then over time the large beaked birds will reproduce more and more, while the smaller beaked birds will reproduce less and less because they can't survive with the food provided. that leads to the trait of small beaks disappearing and the trait of large beaks taking over the island.