如图所示，将一个正电荷从C点分别沿直线移动到A点和B点，均需克

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问题多选题

如图所示，将一个正电荷从C点分别沿直线移动到A点和B点，均需克服电场力做功，且做功的数值相等，则在此空间中，有可能（　　）

A．只存在平行于y轴的匀强电场

B．只存在平行于x轴的匀强电场

C．只在第Ⅰ象限内某位置有一个负点电荷

D．只在第Ⅳ象限内某位置有一个正点电荷

答案

句型转换

同义句转换

1. The soldiers kept working day and night so that they could save more people's lives.

The soldiers kept working day and night ______ ______ ______ ______ more people's lives.

2. To read English aloud every morning is very necessary.

______ ______ necessary ______ ______ English aloud every morning.

3. These questions are very easy. We can understand them.

These questions are not _____ for us _____ ______.

4. The next place that we'll visit is the famous Slender West Lake.

The next place ______ us ______ _______ is the famous Slender West Lake.

单项选择题

从作用力角度分析，在下列渠道中能产生均匀流的渠道为（）

A.平坡渠道

B.正坡渠道

C.逆坡渠道

D.非棱柱形正坡渠道