Imagine That a Group of Researchers Conducted a Single-Blind Study

Imagine that a group of researchers conducted a single-blind study designed to test the effectiveness of subliminal-message weight-loss tapes. Suppose the researchers found that everyone lost weight during the study, even those who were given tapes without any subliminal messages. What could we conclude from the results?

A) The independent and dependent variables in the study are negatively correlated.
B) There is evidence that the study contained confounding variables.
C) There is evidence of a placebo effect.
D) Subliminal tapes are effective in promoting weight loss.