Hurry up, ______ we'll miss the train. [ ]
A. and
B. but
C. or
答案：C
— _____ day is it today?
— It's Tuesday. [ ]
A. What's
B. What
C. Which
风气比的计算必须同时考虑酸气的（）。
A、浓度
B、烃含量
C、浓度和烃含量
D、浓度，烃和胺含量
