在进出口业务中，经过背书能够转让的单据有（）
A.铁路运单
B.海运提单
C.航空运单
D.邮包收据
参考答案：B
Sally is very happy. There is a big smile ______ her face. [ ]
A. on
B. to
C. in
D. at
（）the morning from 0800 to 1200 chief officer is on duty.
A.On
B.In
C.At
D.During
