The best surface to run on is one that's a. as hard as possible so that it adds more stability to your foot. b. hilly so that you can improve your cardiovascular endurance. c. smooth and soft so that it can cushion the stresses of running. d. uneven so that the tendons and ligaments in the ankles and knees are strengthened.

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.