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