You get back into your time machine with your wacky professor and take off again. as your time machine lands, you see an unusual landscape before you. as you open the door you realize you cannot breathe. you quickly shut the door, realizing you are in the
a. late precambrian
b. early mesozoic
c. early precambrian
d. late cenozoic

Which is a direct benefit of prohibiting nicotine and tabacco use in schools?

True or false a fertilized cell divides many times to form an embryo

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.