The balloon has a positive charge and the comb is neutral. The balloon and the comb have the same electrical charge. The balloon has a negative charge and the comb is neutral. The balloon and the comb have opposite electrical charges.
I gave my students this multiple choice question: One student rubs a balloon against his hair several times. Another student passes a comb through her hair several times. The students place the comb near the balloon and observe that the comb repels the balloon. Which is the most likely reason the comb is able to repel the balloon?

Only one answer is correct among these 4 choices:
- The balloon has a positive charge and the comb is neutral.
- The balloon and the comb have the same electrical charge.
- The balloon has a negative charge and the comb is neutral.
- The balloon and the comb have opposite electrical charges.

Could you tell me which one is correct?

The balloon and the comb have the same electrical charge.