This is a test of commonsense. Complete the next sentence:

How to make an electroscope
Gather your materials before you begin.
Any kind of plastic drinking straw will work. It just needs to be long enough to go through both holes in the cup.
Try to center the straw so that there is an equal length on either side of the cup. Use a sharp pencil to poke 2 holes on opposite sides of a styrofoam cup.