读下列四幅地形剖面图，分析回答：

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（2）由此概括出我国地势的主要特点  

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（3）这种地势特征对我国河流流向有哪些影响？

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Equipped with the information they have gathered, they can     preparing their business plan.

A．set out

B．set about

C．set off

D．set up