Which mode in a computer system is used for the execution of normal activities?

User mode is the correct choice for the execution of normal activities in a computer system. In this mode, applications are run with restricted access to the system's core functions and resources. This separation is crucial for maintaining system stability and security, as it prevents user applications from directly interacting with or compromising sensitive system-level processes.

User mode provides an environment where applications can function effectively without the risk of affecting the operating system or other applications. This is particularly important in multi-user environments, where multiple applications may need to run concurrently without conflict. By contrast, kernel mode provides access to the full range of system resources and functions, which is reserved for the operating system's core components and essential services, ensuring that system integrity is upheld.

Maintenance mode and safe mode are typically used for troubleshooting or conducting system repairs and are not considered standard operational modes for everyday user activities. They serve distinct purposes and are only employed when specific issues need to be addressed in the system's operation.