如图是自行车示意图，根据你对自行车的认识，你认为自行车在设计上，为了减小摩擦的是
A.自行车轮胎上的花纹B.自行车脚踏板上的花纹。
c.用橡胶制作自行车的刹车皮D.自行车车轮转轴内的小滚珠
答案：D
A.自行车轮胎上的花纹B.自行车脚踏板上的花纹。c.用橡胶制作自行车的刹车皮（都是增大接触面的粗糙程度，增大摩擦的）D.自行车车轮转轴内的小滚珠（变滑动为滚动可以减小摩擦）选D
Mrs Smith is thirty-eight. She has two ____. She looks very smart with fair and always tries to keep thin. She hopes ___ young and never eats ____ meat. She doesn’t want others to know how ____ she is. Mrs Smith works in an office next to her home. It was raining heavily one morning. The head of ____ office went out to join a meeting. The woman had ____ to do. So she began to talk with Mr Zhang about her birthday party. Mr Zhang is an old man ____ glasses. He works in the same office. ‘My family bought me a fresh cake,’ said the woman. ‘ It smelled very ____ ! And I put nineteen candles on it --- one for a year!’ ‘ Really?’ asked Mr Zhang . He ____ very surprised. ‘ How did you burn ( 点着 ) ____ of the ends ( 两端 ) at the same time? ’
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