A Consumer Reports Group Is Interested in Which Medicine Works

A consumer reports group is interested in which medicine works the best. The researchers take 100 volunteers who experience regular head-aches and who are currently not taking any medications. The Researcher split them into four groups of 25 individuals. Group 1 receives four 100-mg doses of Excedrin each day, group 2 receive four 100-mg doses of Tylenol each day, group 3 receives four 100-Mg doses of Advil each day, and group 4 receives four 100-mg doses of a sugar pill each day. After One week, the researchers compare the number of reported head-aches. If both the individuals in each Group and the researchers monitoring them were unaware of who was receiving which drug, then this Study is said to be

A) a placebo study.
B) a double blind study.
C) a blind study.
D) a census survey.
E) None of the above.