The correct answer is a. The First Amendment of the United States Constitution protects the right to free speech, including the right to express political opinions during elections. In the case of Citizens United v. Federal Election Commission (2010), the Supreme Court ruled that prohibitions on corporate and union independent campaign expenditures were unconstitutional and were protected under the First Amendment. Since the decision, corporations and unions have been allowed to spend unlimited funds on political campaigns, which has led to a significant increase in the cost of elections and in the influence of outside groups on the political process.