Explanation:

- Traditional incandescent bulbs often use Nitrogen along with a small amount of argon. These gases prevent the filament from oxidizing and help maintain the bulb's lifespan.

- Halogen gases, like iodine or bromine, are used in halogen bulbs, not typical incandescent bulbs. These gases allow the filament to run hotter for a brighter light.

- Carbon Dioxide is not typically used in bulbs. It's more common in beverages or fire extinguishers.

- Hydrogen is not used in bulbs due to its highly flammable nature.

Therefore, your understanding is correct. Option 2: Nitrogen is the gas used in traditional electric bulbs.