根据对话内容，用方框中所给词的适当形式填空。(其中有一词多余) follow, bad, first, sports, easy, walk, child, kind What's the coolest kind of transportation (交通工具 ) for middle school students back from the winter holidays? A racing bike? A car? No, it's a special 1 of shoe called Heelys (暴走鞋). Heelys look just like common 2 shoes, but they have a wheel hidden in the heel (鞋跟). So instead of 3 , kids can 'fly' around in them. 'Wearing Heelys is fun and cool,' said Wu Peng, a boy who wore them on his 4 day back at No. 6 Middle School in Beijing. Wu Peng said he loves the shoes so much that he wears them wherever he goes. Sometimes he even 5 his parents' car to the supermarket on his Heelys! Other students think these are very cool, but some haven't been so lucky with their Heelys. It's reported that some 6 have fallen down while using these shoes, and some have been hurt. 'Heelys wheels are on the heels of the shoes, so it's easy to fall,' said Liu Rui, a doctor at the Hong Kong International Medical Clinic, Beijing. Even 7 , Liu said, 'Wearing Heelys for a long time could stop young people from developing their ankles (脚踝) and legs.'