题目

—Has he ever used a dictionary to look up new words while reading ?    —No, ____________. He guesses the meaning all the time .      A. never         B. always       C. sometimes       D. usually 答案：A天然水分别经过下列净化操作后，所得水纯度最高的是（　　）A．沉淀B．过滤C．吸附D．蒸馏