Why is only argon filled inside light bulbs??

Why is argon used in filling electric bulbs?

Argon is an inert gas used in light bulbs to retard the vaporization of the filament. A certain light-bulb containing argon at 1.25 atm and 18^(@)C is heated to 85^(@)C at constant volume. Calculate its final pressure.

Which gas is filled in element bulbs/tubes?