Environment variables are widely used in Linux systems to configure application behavior, and Linux+ V8 emphasizes the distinction between temporary and persistent variables. A variable is persistent only if it is defined in a shell initialization file.

The correct approach is echo "export VAR=value" >> ~/.bashrc. This command appends the variable definition to the user’s .bashrc file, ensuring the variable is set automatically every time the user starts a new shell session. This makes the variable persistent for that specific user.

Options B and C only define variables in the current shell session and are lost when the session ends. Option A incorrectly targets the SSH configuration directory and is not appropriate for defining shell environment variables.

Linux+ V8 documentation highlights .bashrc, .bash_profile, and /etc/profile as correct locations for persistent environment variables. Therefore, the correct answer is D.