How to enable boot option menu in laptop/notbook

Normaly boot option menu can be selected by pressing f12 function key at the time of booting.But in some models of laptops the boot option menu is disabled.
It is very simple to enable the boot option menu

First go to bios setup by pressing f2 function key in some models use escape key.
 
Then go to advanced settings.

In advanced settings there is f12 boot option menu.
Normally it is desable
Select and change the setting to enable.
Use f10 key to save bios setting and exit.
From the next boot the boot option menu can be selected using f12 function key.......

thank   u

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