液相色谱仪检测是通过什么进行定性的（）。A、压力 B、流速 C、保留时间 D、峰面积

环境污染物对人体健康产生慢性危害的根本原因是（）

A.低浓度的环境污染物对机体损害的逐渐积累

B.环境污染物的毒性高

C.环境污染物之间的联合作用

D.低浓度的环境污染物可经口吸收

E.低浓度的环境污染物可经呼吸道吸收

INTERNATIONAL TRADE OF PANLAND

EXPORTS

小题1:Considering all imports and exports, what statement can be made about Panland’s trade?

A．Panland imports food and exports raw materials.

B．Panland imports manufactured goods and exports food.

C．Panland imports manufactured goods and exports raw materials.

D．Panland imports raw materials and exports manufactured goods.小题2:With which of the following does Panland carry on the most trade?

A．Asia.

B．Africa.

C．Middle East.

D．United States.小题3:Judging from its economy, it could be concluded that most of Panland’s working people are _____

A．farmers

B．fishing people

C．unskilled laborers

D．skilled factory workers

斜管出水水质恶化的原因及处理方法？

警察是为全社会服务的，因而是没有阶级性的。( )