The correct answre is D.
Citizens United v. FEC was a case which led to the enactment of a landmark decision by the US Supreme Court in 2010.
The Federal Election Comission, a conservative non-profit organization, broadcasted an advertsiment against the aspiration of Hilary Clinton during the 2008 presidential election. Such ad had an audience superior to 50,000.
The freedom of speech right, guaranteed by the First Amendment to the US Constitution, states that goverment cannot limit communications financed with private funds and performed by nonprofit corporations, for-profit corporations, labor unions, and other associations.
On the other hand, the federal law explicitly prohibits such organizations from "electioneering communication" in the 60 days prior to the election, if these communications reach more than 50,000 people from the electorate. Therefore, the US Supreme Court declared that the Federal Election Comission had acted against the federal law and the US Constitution.