Some cruise ship passengers are given magnetic bracelets, which they agree to wear in an attempt to eliminate or diminish the effects of motion sickness. Others are given similar bracelets that have no magnetism. What type of study is this? What are the variables of interest? Choose the correct answer below.
A. Observational study. The variable of interest is whether the passenger experienced motion sickness.
B. Observational study. The variable of interest is whether a passenger's bracelet is magnetized or not.
C. Experiment. The variable of interest is whether the passenger experienced motion sickness.
D. Experiment. The variable of interest is whether a passenger's bracelet is magnetized or not.