Read the excerpt from "Thomas Edison: The Master of Improvement.” Its glow was produced by electricity passing through a filament, or tiny piece of material. The inside of the glass bulb was a vacuum. Based on context clues, what is the meaning of the word filament?
A:a place where electricity is made
B:a very small piece of material
C:the inside of a lightbulb
D:the vacuum inside a bulb
