There Have Been Several Famous (Or Infamous) Attempts to Manipulate

There have been several famous (or infamous) attempts to manipulate people's attitudes subliminally (for example, Vicary's "Eat Popcorn" demonstration, Wilson Bryan Key's examination of "hidden persuasion" in alcohol ads, and the Bush campaign's "RATS" ad) .One should be cautious when hearing that attempts such as these work, because

A) random samples were not used in these studies.
B) control groups were not used in these demonstrations.
C) these studies were low in mundane realism.
D) experimenter demand may have created the results.