The gas usually filled in the electric bulb is:

Correct Answer: A. Nitrogen

The gases that are commonly used in electric bulbs are argon and nitrogen, helium, and neon. This is because they are inert gases. This means than they are chemically unreactive. This prevents the tungsten filament from damaging fast or getting burn and protects the bulb. Modern bulbs are usually filled with a mixture of argon and nitrogen. More rarely, some bulbs are filled with pure argon, krypton, or xenon.