Where are you going ______ the holiday? [ ]
A. of
B. at
C. to
D. during
答案:D
你了解中国早期的海军学校吗?
正常龈沟的深度是()
A.<0.5mm
B.0.5~2.0mm
C.0.5~3.0mm
D.1.5~2.5mm
E.3.0~4.0mm