Carbon dioxide ___ from burning fuels is the most common of the so-called greenhouse gases.

A．producing

B．having been produced

C．to be produced

D．produced

阴囊及腹股沟内可见液性暗区，与腹腔相连通（）

A．睾丸鞘膜积液 

B．精索鞘膜积液 

C．婴儿型鞘膜积液 

D．先天性交通性鞘膜积液 

E．腹股沟斜疝