All passengers ___ to show their tickets next time. A. require B. will require C. are required D. are to require 答案:C 解析: are required to do(被要求)是被动语态,主动语态是require sb. to do.100 mL 6 mol·L-1的H2SO4跟过量锌粉反应,在一定温度下,要想减缓反应进行的速率,但又不影响生成的氢气的总量,可向反应物中加入适量的( ) A.适量浓H2SO4 B.硫酸钾固体 C.醋酸钠固体 D.硝酸钾溶液