Scientists discovered that stars in the universe are mostly composed of which elements? A. hydrogen and helium
B. hydrogen and oxygen
C. oxygen and nitrogen
D. helium and nitrogen

The image shows the evolution of a species of fish. a few fish from a population developed different social behaviors and evolved into different species. two fish according to the image, the fish underwent . the new species of fish had mating seasons that were different from that of the original fish. because of the differences in mating seasons, the fish underwent reproductive isolation. this mode of isolation would be .