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 between your body and the slide causes a transfer of electrons, resulting in your body (and hair) acquiring a positive or negative charge. The hairs then repulse each other because they have the same charge, causing them to stand up.