He was very rude to the customs officer, ______ of course made things even worse.
A. who
B. /
C. what
D. which
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There were dirty marks on Jim's uniform _____ he had wiped his hands.
A. where
B. which
C. when
D. that
He works in a business _______ almost everyone is waiting to be promoted.
A. how
B. which
C. where
D. that
为了保持公共卫生间的卫生，采用换气次数法选择风机风量，换气次数比较合理的为：
A. 3次/小时
B. 8次/小时
C. 20次/小时
D. 30次/小时
某风机的额定风量为3000ｍ３／ｈ，风压为１０００Ｐａ，在不同的管路中，其风量可能发生变化描述准确的为：
A. 保持不变
B. 只能变大
C. 只能变小
D. 既有可能变大，也有可能变小
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