So ________ that all the living things are dying out gradually. [    ]

A. serious polluted the lake is

B. serious polluted is the lake

C. seriously polluted is the lake

D. seriously polluted the lake is

流动性差的水渣易在锅炉热负荷高或（）的地方沉积下来，再次形成二次水垢。

A.锅水循环较快

B.蒸汽流动较快

C.锅水循环缓慢

D.蒸汽流动缓慢