Not until all the fish died in the lake __________ how serious the pollution was.

A．did the villagers realize

B．the villagers realized

C．realized the villagers

D．do the villagers realize

CO₂潴留时可出现以下哪些症状或体征( )

A．昏睡、昏迷

B．腱反射消失，锥体束征阳性

C．皮肤温暖、多汗

D．神志淡漠

E．扑翼样震颤或肌肉震颤