Final answer:
Payment of salaries is an internal event within a business.
Step-by-step explanation:
An internal event refers to a business transaction or activity that occurs within an organization. Among the options provided, the most appropriate answer is payment of salaries.
While the use of supplies, repayment of a note payable, and payment of rent expense are all financial transactions, they involve external parties and are considered external events.
Payment of salaries, on the other hand, does not involve any external parties and is solely an internal event as it represents the compensation being made to employees within the organization.