砌筑砖拱碹，灰缝呈放射状，每道灰缝应与弧形胎膜的对应点的切线

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问题单项选择题

砌筑砖拱碹，灰缝呈放射状，每道灰缝应与弧形胎膜的对应点的切线相垂直，下部的灰缝不小于（），上部的灰缝不大于15mm。

A、2mm

B、5mm

C、10mm

D、12mm

答案

参考答案：B

选择题

为了研究影响平行板电容器电容的因素，设计如图实验．实验中，使电容器的两个极板A、B分别带上等量异种电荷，并将A极板和静电计的外壳分别接地，如图所示，若保持极板所带电荷量不变，下列判断正确的是（　　）

A．A板稍微上移，静电计指针张角变大

B．增大两极板之间的距离，静电计指针张角变小

C．将A板向右移少许，静电计指针张角不变

D．将玻璃板插入两板之间，静电计指针张角变大

填空题

用单词的正确形式填空

1. He happened __ __(help) an old woman on his way home.

2. I have forgotten____(return) his money, so he didn't receive.

3. I spent about half an hour in____(write) yesterday's diary.

4. She was very busy, so I let her____(go) back first.

5. At least we can afford ____(buy) an electric bike.

6. I had something to ask him, but he avoided___ ( answer) my question.