The correct answer to this question is C. They move closer together. This question is related to electric force and electric charge. One of the fundamental concepts of this study is negatively and positively charged items are attracted to each other.
Therefore, the slightest contact they come in with each other, they will move closer together. This is why the leaves would move closer to one another because positives and negative forces attract to each other.
If they were any other force combinations, they would move away from each other instead of coming close together. This question would be likely to be asked on a science test.