What command is used to add a new user to the system?

The command to add a new user to the system is "useradd username". This command directly instructs the system to create a new user account with the specified username. It is a standard utility available in many Linux distributions and is the most basic command for user creation, allowing for different options to customize the new user’s settings.

Using this command creates a user account with default settings. However, it's important to understand that "useradd" alone does not automatically create a home directory for the user; that is typically a feature of the "-m" option, which tells the command to create the user's home directory upon account creation. Therefore, while option B is correct, utilizing option D (useradd -m username) would also result in adding a user with a home directory, offering more functionality.

In contrast, the command "adduser username" is often a front-end to "useradd" that may vary in implementation depending on the Linux distribution, sometimes providing more interactive prompts. The "newuser" command is not a standard command found in most Linux distributions, so it would not work for adding a user. It's beneficial to note these distinctions to understand the variations and options available when managing users in Linux.