The statement that best explains why your hair stands up after sliding down the plastic slide is:
Friction causes a transfer of electrons between the slide and you, making each of your like-charged hairs repel each other.
When you slide down the plastic slide, friction causes electrons to transfer between the slide and your body. This process can result in your body becoming negatively charged (or positively charged depending on the materials in contact), leading to like charges on your hair. Since like charges repel, your hair stands up as it tries to get as far away from each other as possible.