Help me and get me the answer

Consider the following three studies: Study 1) You want to know if pet ownership affect heart attack reoccurance. You receive a list of all heart attack victims from the local hospitals and randomly sample 120 of them. You record whether or not they have a pet at home, and then track whether or not they have another heart attack within five years. Study 2) You work for a pharmaceutical company with a new migraine medication that you wish to test the efficacy of. You randomly assign 60 migraine patient volunteers into three groups. 20 of them receive a sugar pill with no medication, 20 of them receive a pill with a half dose of the medication, and 20 of them receive a pill with the full dose. None of the patients are informed as to which group they are in. You then ask the patients to report on both the frequency and severity of their migraines over a one month period. Study 3) You are curious if having 'organ donor' as the default on licence registration affects whether or not people would agree to become an organ donor. You perform an experiment with student volunteers, and tell all the subjects to imagine moving to a new state and having to apply for a license. You then randomly assign subjects to receive a registration form to fill out that either asks them to check a box to agree to be an organ donor (not default) or asks them to check a box to opt out of becoming an organ donor (so organ donor is the default). For which of the studies can you make a cause and effect conclusion? | FSe!ect ] feisiis ii = = = = = ; = = = S 7\\ Which of these studies was blind? = [Select] [T e =) Which of these studies used a placebo?| [Select] 1 5 == = Which of these studies used a comparison grpupu? | [ 73[?'?(]7 7 N v Which of these studies used random sampling? [Se!e??;]