_____ we were singing, the teacher came in.
A．Before
B．after
C．As
D．Until
答案：C
--I can't find Mr. Smith.
--It was in the hotel___________ he stayed.
A．that
B．where
C．which
D．since
《天津条约》签订于（）年。
A.1858年
B.1859年
C.1860年
D.1861年
