Final answer:
Political action committees (PACs) are regulated by the Federal Election Commission (FEC) and must disclose the source of their funds.
Step-by-step explanation:
In the context of federal law, political action committees (PACs) are regulated by the Federal Election Commission (FEC) and must disclose the source of their funds. Therefore, option d. There are no limits on donation amounts, but the donors cannot be anonymous is the best description of PACs in the context of federal law.