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 ?

What is the best way to use the clean water act to address the issue of dirty water and diseases that plague asmall community? a) to report the number of cases of people who havecholera symptomsb) to provide health guidelines about effects from waterborne diseases c) to enforce standards that focus on chemical dischargeinto bodies of waterd) to carry out research that investigates how dirty wateraffects human health