同学们,我现在不但能熟练地骑自行车,还知道它的构造和功能呢。今天我就向你介绍介绍自行车的构造和功能。自行车包括龙头、大杠、车轮、齿轮四大件。它们的任务不同,作用也不同。龙头是自行车的“指挥部”,生就了一种倔强的性格,左不得,左不得,永远向正前方,决定着前进的方向 My classmates, I now not only skillfully ride a bicycle, but also know its structure and function of it. Today I introduced to you about the construction and function of bicycles. Bicycles include faucet, big bar, wheel, gear four big pieces. They have different tasks and different roles. Bibcock is the bicycle “command”, gave birth to a stubborn character, can not be left, can not be left, always to the front, determines the direction of progress