Final answer:
Tungsten is used as a filament in light bulbs primarily because it sublimes slowly at high temperatures, allowing it to emit a bright, white light over a longer period without degrading rapidly. Its ability to withstand high temperatures without melting or burning adds to its suitability as a filament material.
Step-by-step explanation:
Tungsten is most often used as the filament in light bulbs because it has a combination of properties that make it an ideal choice. The correct answer to the question is D. it sublimes slowly at high temperatures. Tungsten filaments can operate at high temperatures (up to 2900 K), and when heated to such temperatures, they emit a broad spectrum of light, which includes all the visible frequencies, thus producing a light that appears white to our eyes. Tungsten's high melting point means it can get very hot and glow brightly without melting, and its ability to sublime slowly allows the filament to last longer without breaking down.
Also, when operated in a light bulb, the tungsten filament is not exposed to oxygen because bulbs are either evacuated or filled with inert gas to prevent the filament from burning. This extends the lifespan of the filament, allowing it to maintain the high temperatures necessary for white light production over a reasonable lifetime. Thus, while other options might have some relevance, the fact that tungsten does not evaporate quickly at the operating temperatures of a light bulb is the most significant factor for its use as a filament.