动式染毒主要优点是（）

A.装置备有新鲜空气补充

B.受试化合物保持浓度不变

C.保证染毒柜内和二氧化碳分压恒定

D.温湿度恒定

E.以上都是

So far we have done a lot to build a lowcarbon economy, but it is _____ideal. We have to work still harder.[ ]

A. next to  

B. far from

C. out of 

D. due to