A user’s laptop screen is extremely dim. A technician attempts to alter the brightness using
function keys and the BIOS, but the screen never changes in brightness. Which of the
following is MOST likely the cause?

A.
Battery failure

B.
Bulb failure

C.
Display driver is corrupted

D.
Backlight failure

Explanation:

http://www.laptoprepair101.com/laptop/2007/09/05/troubleshooting-laptop-with- backlightfailure/