A 24-year study of 1,500 adults showed that those subjects with a high intake of foods rich in beta- carotene were mu...

Anita on May 1, 2018

Yes, D suggests that in the study, there was a placebo. However, with no results showing anything one way or another, the placebo effect seems to not exist in this case. There were no differences at all!

E shows another way that there could have been differences between the high-BC population and the low-BC population. It could be, essentially, that the high-BC population also had other healthier habits that reduced their risks of cancer and heart disease, such as smoking less.

Filippo on May 21, 2020

While I selected it through process of eliminaiton, I don't quite understand why D is correct from the explanation above. Could anyone explain it again please? Thank you!