【简答题】阅读材料,完成下列要求。(12分) 材料 近年来,食品药品安全事件考验着国民的承受力。“山东疫苗事件”,3.15央视曝光的网络订餐平台黑心作坊事件、有毒辣条事件......这一桩桩事件,深深地刺痛了国民的心灵,同时也考验着国家的监管能力。对此,相关部门也在不断加大治理的力度,比如,近日沪检方提起危害食品药品安全犯罪案件公诉261件330人,北京市食药监局与外卖平台合作打击无证餐饮,国家食药监总局发...
【简答题】基本表结构修改用_____________语句,基本表内容修改用___________语句
【单选题】SQL语言使用( )语句修改基本表结构。
【单选题】下列SQL语句中,修改基本表结构用的语句是
【单选题】The purpose of DC generator brushes is to ().
A.
neutralize armature reaction
B.
conduct electric current to an outside circuit
C.
convert DC current to AC current
D.
provide excitation to a DC generator
【单选题】When the generator overloads in an automatic electric power plant, ______.
A.
the stand-by generator set will start and synchronize automatically
B.
the ACB of generator will trip
C.
the windings of generator will burn out
D.
the whole ship will lose power
【单选题】Which of the following is true of an asynchronous generator?
A.
The generator uses brushes and slip rings
B.
The rotation and driving frequency are the same
C.
Permanent magnets are used
D.
There is no electrical connection to the rotor