The ancestors of elephants inhabited every continent except antarctica and australia. but the asian and african elephants are the only ones to survive. why?

a) dinosaurs killed all other elephant species.

b) asian and african elephants killed off other species of elephants.

c) asian and african elephants adapted well to their environments.

i think it is dna, i'm not totally sure but i think it might be.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.