In UNIX, a program that runs in the background (not 
attached to a terminal) is called a "daemon." It's 
something you can't see, but it's alive and well doing work 
behind the scenes.

Daemon stands for Disk and Execution Monitor. A daemon is a 
long-running background process that answers requests for 
services. The term originated with Unix, but most operating 
systems use daemons in some form or another.

daemon is a computer program that runs in the background, 
rather than under the direct control of a use

semaphore uses one thread .so it can access little slower 
than ordinary variable.

Semaphore variable is used under 'n' process solutions to
handshake mutual exclusion rule, where as ordinary variable
is used such circumstance is error prone if set that
variable as boolean type even you get problem while setting
value to parent thread.

where n>1 

check it out!

4.None of the above

3)time sharing

2)security

virtual memory

time sharing

Critical Section comes in single process environment they
didn't share accross process boundary.

In C if you wish to implement criticalsection you have to
use windows datastructure CRITICAL_SECTION and create a
object to access its members.

Initialize it
  InitializeCriticalSection(&cs);
------------
-----------
function to call();
------------
DeleteCriticalSection(&cs);
.
.
call()
{
}

Now sure what is asked but anyway:
1. If the question is how would you implement critical 
section mechanism then the answer is to use a mutex.
2. If the question is to show how to use the critical 
section then the following code fragment adresses that:
//
//  Global variable or a member of some
//  dynamically allocated structure, usualy within
//  the data access to which it is protecting.
//
CRITICAL_SECTION cs;

VOID Init(VOID) {
   InitializeCriticalSection( &cs );
}

VOID SomeCall(VOID) {
  EnterCriticalSection( &cs );
  //
  //  Thread-safe block of code protected by critical 
section.
  //
  LeaveCriticalSection( &cs );
}

VOID
UnInit(VOID) {
  DeleteCriticalSection( &cs );
}

Go to TaskManager,

Select Applications tab and select EndTask.
                   (or)
Select Process tab and select EndProcess.

U can kill a particular process in windows by pressing 
Ctrl+Alt+Delete-->Click on Task Manager button-->and select 
the program which one you want to kill and click on End 
Task button.

using Debuggers we can kill with the command .kill