精液标本送检应于采集标本后（）。
A.10分钟内
B.20分钟内
C.30分钟内
D.40分钟内
E.50分钟内
参考答案：C
— What's the matter?
— I am having trouble ______ who has taken my book. [ ]
A.finding
B.looking for
C.finding out
D.looking up
功能良好的牙齿，牙周膜间隙的宽度为
A．0.18～0.25mm B．0.5mm C．0.5～0.8mm D．1.0mm E．1.5mm
