保证产品达到规定的功能和技术要求所必须的材料损耗属于（）。A.工艺性损耗 B.非工艺

阅读短文，判断正(√)误(×)。

      Lily is a student of No. 16 Middle School. She's good at English. Her teacher likes her very much. She

often lets her show the visitors around. Lily likes doing that. She often introduces the class building, the library,

the computer room and the music club to them. She likes her school a lot.

( ) 1. Lily is a teacher.

( ) 2. Lily enjoys speaking English.

( ) 3. Lily doesn't like show the visitors around.

( ) 4. She often introduces the dance room.

如图，AD垂直平分线段BC于点D，连接AB，∠ABC=60°，BE平分∠ABC，交AD于点E，连接EC，则∠CED的度数为______．

冬天人们用热水袋取暖利用了水比热最大的特性，水的比热是______J/（kg•℃）．若热水袋内水的质量为1kg，初温为90℃，过一段时间，温度降低了50℃，则水放出的热量为______J．

（）过量可导致小鼠繁殖紊乱和胚胎畸形。

A.维生素A

B.维生素C

C.维生素B族

D.维生素D

19世纪末20世纪初，世界市场形成和发展的主要原因包括（）

A.第一次世界大战的爆发

B.欧美国家的殖民扩张

C.马克思主义学说的传播

D.工业革命和科技的进步