Final answer:
Schedule 13D must be filed with the SEC within 10 days of acquiring beneficial ownership of more than 5% of a company's equity securities (B).
Step-by-step explanation:
Under U.S. securities law, when an investor or a group acquires beneficial ownership of more than 5% of a voting class of a company's equity securities registered under section 12 of the Securities Exchange Act of 1934, they are required to file a Schedule 13D with the Securities and Exchange Commission (SEC). According to this regulation, the Schedule 13D must be filed within 10 days of the transaction. Therefore, the correct answer is 10 days, the SEC.
Schedule 13D must be filed within 10 days of acquiring the stock, and be filed with the company.