牙科清洁材料是通过什么去除表面污物的（） A.物理的作用 B.机械清除 C.化学作用

据美国地质勘探局网站消息，智利西部沿海北京时间2014年4月2日7时46分发生8.2级地震，已经引发2米高海啸。美国国家海洋和大气管理局随后发布海啸传播时间预测图，预测图显示，此次地震引发的海啸最快18小时后抵达澳大利亚，21小时后抵达日本。本次地震带位于哪两大板块交界处。

A．美洲板块与南极洲板块

B．美洲板块与亚欧板块

C．美洲板块与太平洋板块

D．美洲板块与印度洋板块

判断正（T）误（F）。

     Fruit and vegetables should be a part of what we eat every day. Educating your children about the

importance of eating fruit and vegetables is important for their health. Here are some fun activities to

help you teach your children about fruit and vegetables.

     ★ Reading is one excellent way. Choose a colorful book with many different types of fruit and vegetables.

     ★ Provide your children with fruit and vegetable puzzles. Your children will be able to see what fruit and 

vegetables look like as they're putting the puzzles together. You can also teach them the different names of

fruit and vegetables.

     ★ Each day give your children different fruit and vegetables to eat. This will give them the chance to

taste many kinds of fruit and vegetables. Talk to your children about what they look like and how they taste

and smell.

     ★ Play fruit and vegetable games. Prepare little cups with fruit and vegetables cut up into small pieces.

Cover your children's eyes and give them one of the cups to try. After tasting, they have to guess what kind

of vegetable or fruit it is.

     ★ Grow vegetables. You can teach your children how vegetables grow by planting them. Your children

will also learn how to take care of vegetables.

( )1. Reading is a good way to help your children know about fruit and vegetables.                 

( )2. The puzzles can help children know how fruit and vegetables taste and smell.                

( )3. By playing fruit and vegetable games, children can know what fruit and vegetables look like.

( )4. Growing vegetables can teach your children how to look after vegetables.                    

( )5. The passage is mainly about the advantages of eating fruit and vegetables.                  

（）是收集一手资料时最普遍采用的手段。

A.问卷

B.座谈

C.电话

D.邮寄

按照我国规定，对实行法定商检的商品，应( )。

A．先报检，后报关
B．先报关，后报检
C．先放行，后检验
D．检验与海关查验同步进行

工件圆周速度与砂轮圆周速度（）

A、成正比

B、成反比

C、无关