单项选择题
1、 fle也d等于(    )．
A．
B．
C．
D．


2、根据下面内容，回答题：
Never laugh at a snow covered mountain! Laughter and yelling, during the avalanche season, can cause a deadly pile of snow. Huge snow slides are most common in mountains where there are steep slopes that are well buried in snow and ice. The snow builds up slowly and lands very softly. This can create a very touchy, unstable situation. Tons of snow may be held up by only the friction between snowflakes: The deep snow is like a house of cards. The slightest movement can cause it to fall. As soon as something slips, this great mass of snow will come crashing down the mountainside.
Slides may be started by sound vibrations. They may also be started by the weight of wet, melting snow. Once an avalanche has been triggered, the cause no longer matters. Moving down a steep slope,it picks up great speed and added snow. Some avalanches travel as fast as two hundred miles per hour.
The. force of an avalanche will mow down anything in its path. Whole houses have been swallowed up by these fast-paced piles of snow.
The wind that is caused by an avalanche is almost as destructive as the snow itself. Winds from an avalanche have been known to travel as fast as those of a tornado. So, when approaching a thickly snow covered mountain, speak softly!

Avalanches can be started by________.
A．falling snow
B．the wind
C．loud sounds
D．friction between snowflakes


3、 杨某将一辆货车作价2万元抵押给孙某，并依法进行了抵押登记，该货车继续由杨某使用。一日杨某在运输途中不慎翻车，造成货车报废，保险公司依保险合同赔偿杨某损失3万元。则（　　）。
A．应认定杨某与孙某的抵押关系解除
B．应认定杨某与孙某的抵押关系终止
C．应认定抵押关系继续有效，应以保险公司赔偿的3万元作抵押
D．应认定抵押关系继续有效，应以保险公司赔偿的2万元作抵押


填空题
4、


简答题
5、阶级斗争是社会发展的直接动力。


6、简述群落的水平结构及其复杂性的原因。


7、  求微分方程y″+3y′=3x的通解．


8、你(Li Yuan)听说你的好朋友(Mike)通过了考试，可以上大学了。发一封电子邮件表示祝贺。邮件的内容如下：
(1)表示祝贺；
(2)祝贺的方式。

9、

判断的敛散性

10、

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