关于窝沟封闭剂的保留率正确的是（） A.下颌牙比上颌牙高 B.年龄小比年龄大高 C.

下列是初中化学部分重要的实验或实验装置。请按要求填空：

（1）A实验玻璃管②中产生的气体是                                   ；

（2）B实验如果实验数据小于21%，可能原因是              、                （写出两点）；

（3）C实验说明二氧化碳具有的性质是                        、                          ；

（4）写出用D装置制取二氧化碳气体的化学方程式                                         。

根据《建筑设计防火规范》的厂房（仓库）火灾危险性分类规定，下列属于生产的火灾危险性为甲类厂房的有（）

A.乙炔站

B.黄磷制备厂房

C.氧气站

D.卷烟包装厂房

根据句意及首字母提示，补全句中所缺的单词。

1. Look at the s________ of an elephant. It's amazing.

2. We c________ with each other mostly by e-mail.

3. We can learn by e________ that oil and water will not mix.

4. He is f________ with Chinese ancient history.

5. At the entrance of the street there is a "No E ________" sign.

6. If you paid more a________ in class, you might actually learn something.

7. "Sit!" he said, and the dog o________ him instantly.

8. The truck s________ up going down the hill.

9. The difference between h________ and animals is that the former one can make tools but the latter

    one can't.

10. After supper his parents always go d________ to have a walk and Tom goes u________ to do his

      homework.

土地改革时，分给农民并颁发土地所有证的土地归（）所有。

A.集体所有

B.集体所有制单位

C.国家所有

D.全民所有制单位

以下哪些情况下，道路货物运输承运人可以免除赔偿责任（）

A.因不可抗力造成货物损毁

B.因货物本身的自然性质造成损毁

C.因收货人的过错造成货物损毁

D.因驾驶员操作不当造成货物损毁