A Study Included 60 People Suffering from an Ordinary Headache

A study included 60 people suffering from an ordinary headache. Twenty received aspirin, 20 received a sugar pill that looked like aspirin, and 20 got nothing at all. In 65 percent of the aspirin group, the headache disappeared. In the other two groups the "cure" rates were 35 and 5 percent, respectively. Other than the drug condition, the participants were treated identically. This study:

A) demonstrates a double-blind design.
B) is an experimental study.
C) contains an important confound.
D) has three dependent variables.