Final answer:
Employees of JL Group use a user interface to interact with the database of the company without needing knowledge of its structure.
Step-by-step explanation:
The employees of JL Group who use the database of the company for their daily work, without having knowledge of how the underlying database is structured, interact with the database through a user interface. This user-friendly interface allows them to perform their tasks without the need to understand or directly interact with the database structure itself. Therefore, the correct answer is (3) Through a user interface.