搜题请搜索小程序“爱下问搜题”
问题 填空题

桂林山水甲天下，山中有水，水中有山…．从物理学角度看，山在水中的倒影是 ______像（选填“虚”或“实”），像的成因是 ______．

答案

平静的水面相当于镜面，倒影是由于光的反射，山在水中所成的虚像；

故答案为：虚，光的反射．

阅读理解

Many children think mobile phones are cool. They come in fun colors and let you talk with friends anytime and anywhere.

In the U.S., more than 90 million people use mobile phones. Many of these people are children. For children, mobile phones are more than phone calls. They are fashionable.

Most mobile phone users don’t think about the health problems caused(引起) by mobile phones. Some scientists say that mobile phones give off radiation(辐射) that might be bad for the users. One newest study shows that mobile phone radiation might raise(增加) a person’s chance of getting some kinds of cancer(癌症). Other scientists say mobile phones don’t’ threaten people’s health. They say that they have not found any link(联系) between phone use and cancer.

Scientists say that people can protect (保护) themselves from mobile phone radiation. One way is to use a headset(耳机). Or people can make shorter call.

小题1:Many children like mobile phones because they think mobile phones are _________.

A．cool

B．small

C．cheap

D．their toys小题2:Many of the mobile phone users in the U.S. are ___________.

A．girls

B．boys

C．scientists

D．children小题3:Some scientists think mobile phones aren’t _________ for users health. They causes some kinds of cancer

A．bad

B．good

C．wrong

D．helpful小题4:The underlined word “threaten” in the passage means ____________.

A．威胁.

B．担心

C．治疗

D．证实小题5:What should people do to protect themselves from mobile phone radiation?

A．Make longer calls

B．Use a headset

C．Make shorter calls

D．Both B and C
查看答案
选择题

20℃时，KCl的溶解度为34g，若忽略固体溶解引起的溶液体积变化，则在该温度下，所配KCl溶液中KCl的物质的量浓度不可能是                        （   ）

A．2mol/L　

B．3mol/L

C．4mol/L

D．5mol/L
查看答案