石灰稳定土基层施工期间的日最低气温应在（）以上并应在第一次重冰冻到来之前完成。 A.

世界上经济发展水平最低的大洲是：[ ]

A．亚洲

B．欧洲

C．非洲

D．大洋洲

2011年3月11日，日本强震导致福岛核电站发生核泄漏，产生具有放射性的对人体和环境有害的。下列有关叙述正确的是 （  ）

A．中含有131个电子

B．同周期元素中碘原子半径最大

C．大量食用加碘食盐可以有效抵御核辐射

D．原子最外层有7个电子

实验室鉴定氯酸钾晶体和1－氯丙烷中的氯元素，现设计了下列实验操作程序：①滴加AgNO₃溶液；②加NaOH溶液；③加热；④加催化剂MnO₂；⑤加蒸馏水过滤后取滤液；⑥过滤后取滤渣；⑦用HNO₃酸化。

（1）鉴定氯酸钾中氯元素的操作步骤是                                （填序号）。

（2）鉴定1－氯丙烷中氯元素的操作步骤是                             （填序号）。

阅读理解。

     Children actually are pretty smart and most people just don't give them enough credit. I bet another thing

that you never realized is that children have actually invented several different things. I am going to list 4 of

my favorites, but there are many more available.

Toy Truck

     Can you believe that a 6-year-old boy invented it in 1963? His name was Robert Patch. He created a toy

truck because he wanted a truck of his own that he could take apart and put back together. He first drew

up a sketch of the truck on paper before he got help in getting a patent.

Television

     We all know the first TV came out in the late 1920s. This is something that everyone has already known,

but did you know the TV was invented by a 14-year-old boy? It took him several years to get the idea in

motion, but he did it. A teenager came up with something every household owns today.

Popsicle (冰棒)

     This is something that you may think a child probably invented, but you never knew for sure. Back in the

early 1900s an 11-year-old boy named Epperson had an idea to make his own version of pop. So he worked

outside on a cold day and he couldn't get his mixture right. He left his glass filled with his idea and stirring

stick, and went to bed. When he came back outside it was frozen on the stick. The first Popsicle named the

Epsicle came into being.

Braille (布莱叶盲文)

     This is something that I find truly amazing. Louis Braille, born on January 4, 1809, came up with this great

idea because he was blinded in an accident when he was three years old. When he was 15 years old he was in

blind school and created what we all know as Braille. This is something that has helped millions of blind people.

1. According to the author we learn that _____.

A. parents always think highly of their children

B. few inventions were created by children in history

C. children's inventions were known to most people

D. most people usually underestimate children

2. What is the characteristic of the toy truck that little Robert invented?

A. It is easy to operate and can run by itself.

B. It is big enough for a kid to get into.

C. It can be taken apart and put back together.

D. It is just like a real truck and runs fast.

3. What can we learn about Epsicle's inventing the first Popsicle?

A. He invented the first Popsicte by chance.

B. He put a glass of mixture outside on purpose.

C. He put a stick in the glass to make a Popsicle.

D. He made use of cold weather to make a drink.

4. Which invention made by the young inventor is the earliest one according to the passage?

A. Popsicle.

B. Toy Truck.

C. Television.

D. Braille.

完颜亮迁都的原因及意义是什么？