题目内容

毛笔蘸上水，笔毛就会粘在一起，这是因为 ( )

A. 笔毛上的水在空气中有自动收缩减小表面的趋势
B. 笔毛被润湿
C. 水是表面活性物质
D. 水具有粘度

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定体积的水，当聚成一个大水球或分散成许多水滴时，同温度下，两种状态相比，以下的性质保持不变的有( )

A. 表面能
B. 表面张力
C. 比表面
D. 液面下的附加压力

Listen to the recording again and fill in the gaps. IKEA offers [1] _____ goods in Shanghai, Moscow, New York and London. The company's [2] _ is to concentrate on the 267 existing stores and [3] ___ them. At the moment Europe leads the market with 80% of sales, followed by North America with 15% and Asia with 5%. IKEA needs to [4] _ its position in the Russian and Chinese markets. Both of these markets have [5] _ for IKEA.There are a lot of people there who do not [6] ________ so much, which is perfect for IKEA's concept.

对齿轮传动的两个基本要求是什么？怎样实现？、。

齿轮传动的有点有：。