C3H8在氧气中完全反应的浓度是( )。
A.32.42%
B.2.75%
C.16.7%
D.4.01%
参考答案:C
Between the two parts of the concert is an interval, __ the audience can buy ice-cream.
A.when
B.where
C.that
D.which
教学档案包括:()
A.教学日程
B.教学制度
C.教研活动记录
D.实习生考勤记录