Final answer:
The shell used for Single user mode is typically bash, as it provides a versatile environment for system administration tasks in maintenance mode.
Step-by-step explanation:
The shell used for Single user mode is typically bash, which stands for Bourne Again SHell. It is a widely used default shell on Linux and UNIX systems. Single user mode, also known as maintenance mode, is used for system administration tasks such as repairing file systems, recovering lost data, or changing system passwords without the interference of multi-user processes. In this mode, the system boots into a single superuser environment, which is typically root, and it often defaults to bash because of its versatility and widespread use.