Which type of study best describes the following research most likely to be done?

a researcher is testing new weight loss supplements. the researcher decides to sample two groups. the first group of subjects, the researcher labeled group 'a'. the researcher plans to give a placebo that looks like the real medicine but is just a sugar pill to group 'a'. the second group, group 'b', will be given the real medicine. the researcher knows which participants got the placebo and which received treatment but the participants don't know.

group of answer choices

blind study

double blind study

open study

closed study