Final answer:
The element with the highest melting point used as a filament in light bulbs is tungsten, which has the symbol W and is known for emitting white light when heated.
Step-by-step explanation:
With the highest melting point of any pure element, tungsten is the filament in ordinary (incandescent) light bulbs. The correct answer to the question is a. Tungsten. Tungsten, with its one-letter symbol W, comes from the name wolfram. This heavy metal is chosen for light bulb filaments because when it is heated to high temperatures, it emits a white light that contains virtually every frequency, ideal for our lighting needs. The very high melting point of tungsten allows the filament to operate at high temperatures without melting, which is crucial for the longevity and functionality of incandescent bulbs.