任务型阅读
根据短文内容，从短文后的五个选项中选出最佳选项填入文中相应的位置。
下面文章中有5处（第71—75题）需要添加小标题。请从以下选项中选出符合各段意思的小标题。

Have you ever rubbed(擦) your hands together when they get cold? Why do we do that? We do that for friction(摩擦). Friction happens when two things that aren’t very smooth rub together to make heat energy. The faster you rub two things together, the more friction (and heat) you can make. Let’s discover friction!
●________小题1:__________
Soap        Water         Your hands
●________小题2:_________
(1). Make sure your hands are dry.
(2). Rub your hands together until you feel the heat of your hands.
(3). Now, use soap and water to get your hands very slippery(滑的).
(4). Try to make friction happen while your hands are slippery.
(5). Please write down what has happened.
●________小题3:__________
Friction is an energy that happens when two things rub together. When friction happens, it makes heat! When your hands are slippery, they won’t make very much friction and your hands won’t get so hot.
●________小题4:_________
(1). Friction happens when you stop your fast running bike.
(2). Ancient people made fire by rubbing two pieces of wood together. Friction happened though they didn’t know it.
●_______小题5:________
Friction is everywhere. Have you ever noticed situations where friction is happening? If not, ask your parents to take you out in a car. If it is not too hot, touch the tires(轮胎) of the car before and after a short drive to see how much warmer they get from friction.