Drunk driving used to occur _____, but now it is under control. [ ]

A. frequently

B. generally

C. practically

D. gradually

工厂排出的无色废水经测定pH=3．如果往此废水中滴入紫色石蕊试液，溶液变成红色．由于治污染需要，欲将此废水调节为微碱性，可在石灰石、生石灰、铁屑这几种物质中选择 _________ 以达到目的．