I can think of many cases ______ students obviously know a lot of English words and expressions but couldn’t write a good essay. A. why B. which C. as D. where 答案:D①硝基苯 ②环己烷 ③甲苯 ④溴苯 ⑤邻二甲苯 ⑥三硝基甲苯,其中不能由苯通过一步反应直接制取的是(填编号)_________。能够由苯一步反应得到的,写出(其中2个)相应的化学方程式:______________________________________________________。