In 1971, Congress passed the Federal Election Campaign Act. This act requires federal political candidates to reveal the sources of the money used for their campaigns. This money is called campaign contributions. The act also limits the contributions that a person or group can donate to a single candidate. Which of the following is most likely the main force behind the passage of this campaign law?
A Special interest groups wanted to get credit for their contributions to politicians.

B Politicians wanted to show how diverse their contributors were.

C Media companies wanted to find more people and interest groups to pay for advertising.

D People were concerned about what groups were influencing politicians through their contributions.