As mentioned in the text, a Yale researcher (Cohen, 1962) conducted research at a time when the ...

As mentioned in the text, a Yale researcher (Cohen, 1962) conducted research at a time when the local police were very unpopular with the students.
 
  He paid some students relatively little and other students relatively more to write an essay that contradicted their true beliefs about the local police, with whom the student body had experienced unpleasant run-ins. Results of this experiment were noteworthy because they demonstrated that
  a. students offered money thought they were being bribed.
  b. counterattitudinal advocacy can affect beliefs about things that really matter.
  c. behaviors in the world outside the laboratory often contradict previous findings.
  d. in the world outside the laboratory, it is very difficult to change people's beliefs about things that matter.