the height of the wall the number of balloons the attraction to the wall the rubbing action on the wool
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: A student is conducting an investigation on static electricity. The student has three balloons and rubs two of them on a piece of wool. The student then touches each balloon to a wall to observe if static electricity would cause the balloon to stick. What is the independent variable in this investigation?
Possibilities:
- the height of the wall
- the number of balloons
- the attraction to the wall
- the rubbing action on the wool

the rubbing action on the wool