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【多选题】
成本按习性可以划分为( )。A.
变动成本
B.
固定成本
C.
半变动成本
D.
混合成本
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【单选题】硒（Se）是人体中的微量元素，有防癌抗癌作用．饮用含适量硒的矿泉水有益于人体健康．有一种硒的氧化物，化学式为SeO 3 ，其中Se的化合价为（ ）
A.
+3
B.
-3
C.
+6
D.
-6
【简答题】甘草中具有抗炎、镇咳、抗癌作用的成分是
【单选题】Which of the following modulations is for the VHF radio telephone?
A.
G3E
B.
F3E
C.
G2B
D.
F1B
【简答题】结构中有环氧丙烷结构，具有抗癌活性的化合物是
【单选题】Once ARQ communication with the coast radio station has been establ/shed, which of the following exchanges will most likely take place?
A.
The vessel then requests the coast radio station's selcall so that communication can be set up on the appropriate working channel. ’
B.
Since communication has akeady shifted to the working channel, the vessel then transmits the subscriber number and text of the message to be sent for the coast radio station to store and forward.
C.
After exchanging answerbacks with the vessel, the coast radio station transmits.c GA+"．
D.
After exchanging answerbacks with the coast radio station, the vessel transmits“GA+”．
【简答题】简答中心性发绀和周围性发绀的鉴别要点
【单选题】Which of the following characteristics of radio galaxies is mentioned in the passage?
A.
They are a type of elliptical galaxy.
B.
They are usually too small to be seen with a telescope.
C.
They are closely related to irregular galaxies.
D.
They are not as bright as spiral galaxies.
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