15℃时，声音在下列哪种介质中传播得最快[ ] Ａ．空气Ｂ．_爱下问搜题

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问题选择题

15℃时，声音在下列哪种介质中传播得最快[ ]

Ａ．空气　　　　

Ｂ．海水　

Ｃ．钢　　　　

Ｄ．软木

答案

答案：C

填空题

从方框中选词用其适当形式填空。

go home, hello, over there, look like, how old, can't find,
it's time to, excuse me, give … to, let me see

1. Where is my pen? I ______ it.
2. ______. What's the time, please?
3. It's seven o'clock. _______ go to school.
4. It's six o'clock. I must ______ now.
5. This is Jim's ruler. Please ______ it ______ him.
6. ______, Mike. Look at these flowers.
7. Where are the balls? They are ______, under the tree.
8. What's the time, please? ______. It''s four twenty.
9. Lucy and Lily ______ their mother.
10. ______ is your father? He''s about forty.

单项选择题

铅蓄电池在充电过程中，端电压（）。

A.上升

B.不变

C.下降