Final answer:
Form 8-K must be filed promptly under SEC rules to inform investors and the public about important events that may affect a company's financial condition or business operations.
Step-by-step explanation:
Form 8-K must be filed promptly under SEC rules. This means that it must be filed as soon as possible after the event occurs. There is no specific number of days mentioned in the options given.
The purpose of Form 8-K is to inform investors and the public about important events that may affect a company's financial condition or business operations. These events could include things like bankruptcy filings, major acquisitions or disposals, changes in leadership, or other significant events that could impact the company's operations or financial standing.