The correct answer to this question is A. Filament. There are different types of filament, including galaxy and protein filament. However, this specific question is related to electrical filament.
An example is in a light bulb. In that bulb is a small wire that holds the two bigger wires of the bulb together — the filament products light in the light bulb. In incandescent light bulbs, the filaments are made of tungsten.
When a current goes through the filament, the filament then glows. When the filaments were first created in light bulbs, they were made of carbon. Later on, they were changed to graphite and then tungsten.