Which of the following is an example of campaign finance regulation?

Requiring candidates to disclose their funding sources is a fundamental aspect of campaign finance regulation. This requirement promotes transparency and accountability in the electoral process by ensuring that voters are informed about who is financing a candidate's campaign. By disclosing funding sources, candidates provide insight into potential influences on their policies and decisions, allowing voters to make more informed choices at the ballot box. This regulation helps to mitigate the risk of corruption and enhances the integrity of the political system.

In contrast, allowing unlimited donations from foreign entities would undermine national interests and security, while limiting the number of candidates that can run stifles democratic participation. Furthermore, allowing candidates to use personal funds without restrictions could lead to inequities in campaigning, where wealthier candidates have an unfair advantage. Thus, the requirement for disclosure stands as a vital regulatory measure aimed at safeguarding the electoral process.