Is a level of oxygen in the blood that is below normal.

Check all that occur during ventricular systole. a. the av valves open to allow blood to enter the ventricles from the atria. b. the av valves open to allow blood to enter the ventricles from the atria. c. the semilunar valves remain closed throughout systole to prevent backflow of blood into the ventricles. d. the semilunar valves remain closed throughout systole to prevent backflow of blood into the ventricles. e. the semilunar valves open to allow blood to flow into the large arteries. f. the semilunar valves open to allow blood to flow into the large arteries. g. the av valves close to prevent backflow of blood into the atria.

Which action occurs in the third stage of cell division a. the nuclear material of a cell is copied exactly b. the nuclear membrane disappears c. the cell forms two nuclei or d. the nuclear material separates, with half moving to wither side of the cell

Explain what you know about the cause of mental illnesses.