Answer:
d. all instances of a process with the same name matched by a regular expression
Explanation:
In Linux OS there is <em>kill</em> command that you can use to force applications to shut down. When you execute <em>kill</em> command, you are actually sending a signal to the system to force it to terminate the incorrectly behaving application.
The syntax for <em>kill</em> is:
$ kill [signal or option] PID
You have to know <em>PID</em> (Process IDentification number) of the desired process to complete this command.
The <em>pkill</em> command allows you to use advanced <em>regex</em> patterns and other matching criteria. Instead of using the <em>PID</em>, you can now terminate the application by entering the name of its process. For example, to shut down <em>Firefox</em> simply enter the command:
$ pkill firefox
Since it matches the regular expression pattern, you can also enter the name only partially, for example:
$ pkill fire