The only things that made the circuit's light bulb light were the paper clip and the penny. Why is that?

Question

Mrs. Grayson asked her class to bring one object from home to complete the electric circuit that they built in class. Some of the items that students brought are listed below.
paper clip
string
fishing line
pencil
penny

Answer 1

As Michael noted, only the paper clip and penny conduct electricity because they are metals whereas the other items are made from materials that do not conduct electricity in any meaningful quantity. In fact, if someone accidentally grabs a live wire, I have seen advice that one should try to knock them free with a piece of dry wood because grabbing them would simply add you to the circuit.

Answer 2

Because the other items do not conduct electricit.