— Your silence    on recent events surprises me.    

— I think it's better____too little than say too much.    [ ]

A. say    

B. to say    

C. saying    

D. to be saying

根据颗粒物在水中的沉淀特性，将沉淀分为( )。
①自由沉淀②絮凝沉淀③拥挤沉淀④压缩沉淀

A．①②③④
B．①②
C．①③④
D．①②③