《献血法》规定，献血者两次献血的时间间隔不得少于（）
A.一个月
B.两个月
C.三个月
D.四个月
E.六个月
参考答案：E
第一次世界大战中，欧洲战场的重心有三次转移，其顺序是 [ ]
A．南线－东线－西线
B．东线－西线－东线
C．西线－东线－西线
D．东线－南线－东线
— You were not in when I dropped in on you yesterday evening.
— Oh, so sorry. I ____ at the railway station for my sister from Beijing. [ ]
A. waited
B. had waited
C. was waiting
D. have been waiting
