Answer the following question: You are presented with the quiz "What could prevent a light bult from turning on?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "when electricity flows to a light bulb , the light bulb will turn on" and "materials that control the flow of electricity are called resistors". So, what's the best answer to the question?

Choose from:
1). sensory neurons
2). herbicide
3). A resistor
4). focusing a lens
5). evaporation
6). heat energy
7). heating liquids
8). energy barrier
Answer:
3).