______ how to operate a switchboard, I had to ask the office supervisor to show me the correct procedures.
A. Not known
B. No to know
C. Not knowing
D. Having not known
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It's already five o' clock now. Don't you think it's about time______？
A. we are going home
B. we go home
C. we went home
D. we can go home
先用2%醋酸冲洗，继用清水冲洗，再用3%硼酸溶液湿敷，或用5%～10%硼酸软膏外涂E．
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