Helmets serve the important purpose of protecting your head and brain should you get into an accident. They are designed to last a certain number of years and absorb a single serious impact. When you buy a used helmet, you don't know how many impacts it's absorbed and if it's expired...
Father:It is very easy to get a shared bike if you have a smart phone.Find a shared bike through the APP,scan the QR code (扫描二维码) on the bike,unlock it then you can ride.And it's very cheap.How amazing!Mother:We need more rules about the shared bike....