Determine whether the study depicts an observational study or an experiment?

fifty patients with colon cancer are divided into two groups. one group receives an experimental drug to fight cancer, the other a placebo. after one year, the spread of the cancer is measured.

is it observational or experimental ?

Which term defines when one person tries to control another in a relationship? a) dating violenceb) consequencec)limitd) abstinence me plzz : (

How could natural selection best be used to explain the evolution of the white fur of arctic fox

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.