Final answer:
The concept that allows multiple users to simultaneously access databases and use computer systems is called multitasking.
Step-by-step explanation:
The concept that allows multiple users to simultaneously access databases and use computer systems is called multitasking. Multitasking refers to the ability of an operating system to execute multiple programs or processes at the same time. It allows users to switch between different tasks or programs quickly and efficiently.
For example, on a computer with multitasking capability, one user can be editing a document while another user is browsing the internet and yet another user is listening to music. The operating system manages the allocation of resources and ensures that each user gets a fair share of the system's processing power and memory.
Therefore, the correct answer to your question is 1) Multitasking.