劳动者在职业活动中接触职业性有害因素所直接引起的疾病称为 A．职业性多发病 B．工伤

学校组织春游，安排九年级三辆车，小强和小明都可以从三辆车中任选一辆搭乘，则小强和小明乘同一辆车的概率是       。

If you don't know a word, you can _____ it _____ in a dictionary. [ ]

A. look...up

B. look...down

C. look...over

D. look...out

Not until about 2000 BC________________________done.

A．were known of the oldest paintings

B．the oldest of known paintings were

C．the oldest known were painting

D．were the oldest known paintings

消除重复限制自由度的支承，除了去掉多余的支承，还可以将其中的一个改为（）。

A.新的定位元件

B.辅助支承

C.移到其它的定位面

D.缩小支承面积

以下哪一项不是煤烟型烟雾事件的气象条件特点？（）.

A.气温低

B.气压低、有雾

C.风速很小、湿度大

D.有逆温产生