Based on the context provided, the word that best fits the definition of sending a package to your aunt would be:
- **La oficina de correos** (The post office)
When sending a package, it is common to use the services of the post office. The post office is specifically designed for sending letters and packages to different locations. They have the necessary resources and staff to handle mailing services efficiently. Therefore, choosing "La oficina de correos" from the list would be the most appropriate option for sending a package to your aunt.
