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参考答案：对
Before a tank is to be crude oil washed，the oxygen content in the tank must be measured at a position（）.
A.immediately above the level of the oil
B.at the top of the tank
C.in the vent riser
D.one meter from the deck
青年患者，右肺下叶背段见一薄壁空洞，应首先考虑（）
A.肺脓疡
B.肺结核
C.肺癌
D.先天性肺囊肿
E.肺包虫囊肿
