词汇与结构We have to adjust heading to follow the course due to the existence of ________.
A. magnetic north
B. magnetic influence
C. magnetic variation
D. magnetic difference
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词汇与结构The weather is __________, which was sunny in the morning, but gloomy now.
A. bad
B. unusual
C. fair
D. unpredictable
词汇与结构Aviation service units offer pilots weather information gathering from __________.
A. meteorological authorities
B. aviation authorities
C. flight authorities
D. ATC authorities
具有吗啡结构的镇痛药有
A. 阿司匹林
B. 阿扑吗啡
C. 纳洛酮
D. 美沙酮
具有氨基酮结构的镇痛药
A. 吗啡
B. 美沙酮
C. 哌替啶
D. 芬太尼
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