题干
_________ only 20 minutes to go before the train left, I felt uneasy in the taxi to the railway station.
A：For
B：With
C：As
D：Because
答案(点此获取答案解析）
B
_________ only 20 minutes to go before the train left, I felt uneasy in the taxi to the railway station.
A：For
B：With
C：As
D：Because
，则集合
的真子集共有（ ）