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【单选题】
删除student表的"平均成绩"字段的正确SQL命令是( )。A.
DELETE TABLE student DELETE COLUMN 平均成绩
B.
ALTER TABLE student DELETE COLUMN 平均成绩
C.
ALTER TABLE student DROP COLUMN 平均成绩
D.
DELETE TABLE student DROP COLUMN 平均成绩
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举一反三
【单选题】The Vessel is a（）bulk carrier which is permitted to carry grain in bulk without requiring any fittings under the Rules of the 1974 International Safety of Life at Sea Convention.
A.
Self-loading
B.
Self-trimming
C.
Self-unloading
D.
Self-discharging
【单选题】利用多图层作图时,以下哪种操作可以使曲线在Y轴方向上相对变低且曲线靠近X轴:
A.
To值设置成一个比原始值大的数
B.
From值设置成一个比原始值大的数
C.
To值设置成一个比原始值小的数
D.
From值设置成一个比原始值小的数
【单选题】Under the Rules, any vessel may slacken her speed, stop, or reverse her engines to ______.
A.
create a crossing situation
B.
allow more time to assess the situation
C.
attract the attention of another vessel
D.
All of the others
【单选题】Under the Rules, any vessel may slacken her speed, stop, or reverse her engines to __________.
A.
attract the attention of another vessel
B.
avoid to involve in collision danger
C.
allow more time to assess the situation
D.
create a crossing situation
【单选题】【单选】Under the Rules, any vessel may slacken her speed, stop, or reverse her engines to __________.
A.
attract the attention of another vessel
B.
avoid to involve in collision danger
C.
allow more time to assess the situation
D.
create a crossing situation
【单选题】关于 N2O( 氧化亚氮 ) 下列哪项说法是错误的?
A.
麻醉作用弱，单独用于麻醉不够
B.
禁用于肠梗阻，气胸病人
C.
长时间高浓度对红细胞生成系有一定损害
D.
使用时必须给氧，氧浓度大于 20% 即可保证安全
E.
不燃烧，不爆炸，对肝肾器官无影响
【单选题】The vessel is a______ bulk carrier which is permitted to carry grain in bulk without requiring any fittings under the Rules of the 1974 International Safety of Life at Sea Convention.
A.
self-loading
B.
self-trimming
C.
self-unloading
D.
self-discharging
【单选题】Under the Rules, any vessel may slacken her speed, stop, or reverse her engines to ______.
A.
create a crossing situation
B.
allow more time to assess the situation
C.
attract the attention of another vessel
D.
All of the above
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