问题
单项选择题
由周期性的激振力所引起的振动叫强迫振动，在选用悬伸镗削过程中（），都属于强迫振动。
A.前道工序留下的有振动的波纹，扩镗时切屑面积发生了变化，导致振动的发生
B.工件材料硬度差异引起切削力的变化
C.镗杆的刚性差
D.如果孔的加工余量不均匀或者断续切削所引起的振动
答案
参考答案：D
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由周期性的激振力所引起的振动叫强迫振动，在选用悬伸镗削过程中（），都属于强迫振动。
A.前道工序留下的有振动的波纹，扩镗时切屑面积发生了变化，导致振动的发生
B.工件材料硬度差异引起切削力的变化
C.镗杆的刚性差
D.如果孔的加工余量不均匀或者断续切削所引起的振动
参考答案：D
| 阅读理解。 |
| Mr Li teaches Chinese in the USA. He comes back to China every year. He gives us a talk. He says, " K Day in the USA is very interesting. All children like it very much. It is on March 7th. When you go out on that day, you can see children running with kites in the open air (露天). When you look up, you can see different kites in the sky (天空). Some are big, and some are small. They are in different colours. Every kite has a long string (长线). The children begin to run when they get the kites up. Every child has a good time that day." |
| 1. Mr Li is ______. He works in the USA. |
[ ] |
| A. a worker B. an English teacher C. a doctor D. a Chinese teacher |
| 2. Mr Li says something about ______. |
[ ] |
| A. how to study English B. K Day in the USA C. his work in the USA D. playing in the open air |
| 3. March 7th is ______. |
[ ] |
| A. Children's Day B. Teachers' Day C. K Day D. Tree planting Day (植树节) |
| 4. Every kite has ______. |
[ ] |
| A. a short string B. a long string C. the same colour D. the same size (大小) |
| 5. There are ______ kites in the sky on that day. |
[ ] |
| A. all kinds of B. one kind of C. three kinds of D. three |