题目内容

What does the author conclude about the prospects of forestation?

A. Deserts in sub-Saharan Africa will diminish gradually.
B. It will play a more and more important role in people’s lives.
C. Forest destruction in the developing world will quickly slow down.
Developed and developing countries are moving in opposite direction.

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力法的基本未知量是

A. 多余约束力
B. 支座反力
C. 角位移
D. 线位移

去掉联结三刚片的复铰，相当于撤除几个约束

A. 2
B. 3
C. 4
D. 5

超静定结构由于未知数平衡方程数，因此仅靠平衡条件不能确定其全部反力和内力。

超静定结构由于存在多余约束，当周围温度有改变或支座发生移动，转动时结构均将引起，产生内力。