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问题 单项选择题

在双缝干涉实验中，要使其屏上的干涉条纹间距变小，可采取的方法为（）。

A.使两缝间距变小

B.使屏与双缝间距变小

C.把两缝的宽度稍微调小

D.改用波长较大的单色光源

答案

参考答案：B

填空题

用所给动词的正确形式填空。

1. We know the earth _____ (travel) around the sun.

2. Can you see the students _____ (plant) trees on the hill now?

3. —Where's your father?

    —He _____ (clean) the car behind the house.

4. I am sure she _____ (be) a very good teacher in a few years.

5. He wanted my help. So I stopped _____ (help) him.

6. Was Jane very busy _____ (plan) a boat trip with you last night?

7. It is very important _____ (not give) your goldfish too much food.

8. The boss usually makes his workers _____ (work) for twelve hours every day.

9. David _____ (fall) off the tree and hurt his legs a moment ago.

10. Millie, _____ (not frighten) the dog, or it will bark at you.
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单项选择题

下列病毒感染人体后不会引起病毒血症的是（）

A.乙型脑炎病毒

B.腮腺炎病毒

C.ECHO病毒

D.轮状病毒

E.登革病毒
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