What Shell Script command is utilized to mark a variable as exportable?

The command used to mark a variable as exportable is "export." When a variable is exported in a shell script, it means that the variable is made available to any child processes spawned from that shell session. This is important for ensuring that environment variables can be accessed by programs or scripts that are executed later on.

For instance, if you set a variable without exporting it, that variable will only exist in the current shell session. Once you export it, any subprocesses will inherit this variable. This is often used to configure environment settings for applications or to pass necessary data to scripts run in subshells.

The other commands listed serve different purposes. "set" is used to set shell options or to define shell variables, but it does not mark a variable for export. "printenv" displays the environment variables but does not modify them, and "env" is used to run a command in a modified environment but does not export variables. These distinctions underline why "export" is the correct choice for the function of marking a variable as exportable.