The correct answer is: B. .profile
The file that contains a set of instructions which are performed when a user logs in is .profile. It is a shell script that is executed by the Bourne-like shells (bash, ksh, zsh, etc.) when a user logs in. It is typically used to set environment variables, define aliases, and source other files.
The file .exrc is a shell script that is executed by the Emacs editor when it starts up. It is typically used to set up Emacs’s environment, such as the default font and colors.
The file .autoexec is a batch file that is executed by the MS-DOS operating system when a user logs in. It is typically used to set up the user’s environment, such as the default directory and the path to the user’s programs.
The file autoexec.bat is a batch file that is executed by the Windows operating system when a user logs in. It is typically used to set up the user’s environment, such as the default directory and the path to the user’s programs.
Therefore, the correct answer is .profile.