The correct answer is A) Zimbardo did not use a control group.
The major flaw in the research design of the Stanford prison experiment was that Zimbardo did not use a control group.
A control group was necessary to study a particular variable in prison. He had no alternative group to compare and measure the results of the experiment.
Other mistakes he had were that he was part of the experiment. He participated as the prison superintendent. He was an authoritative figure inside the experiment of the prison and influenced the behavior of his students. He should have a neutral position.
Answer: the affluent society.
<em>The Affluent Society</em> is a book by economist John Kenneth Galbraith, in which he describes the way in which the United States' economy operated in the 1950s. He argues that the country became wealthy in the private sector but poor in the public sector. Galbraith argued that the government needed to invest on social infrastructure using funds from taxation if it wanted to remain ahead.
This was actually a very smart behaviour. This way the law was accessible to everyone so on one hand, noone could say "I didn't know" and on the other hand it could be used for reference by anyone and people would not need to seek council in every matter. This also decreased the possibility to abuse power (if the law was only accessible to few, those few could abuse their power by manipulating it in their favour).