She read the instructions to find out how to _______ the computer.

            [ ]

A. use                    

B. to use

C. using                    

D. uses

离子色谱法测定废气中氯化氢时，所用去离子水的电导率应小于1μS／cm，并要经过0.6μm的微孔滤膜过滤。