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【简答题】
修改 users 表 第二列 sex ,由可以为空改为不可为空。
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【简答题】气门传动组的作用是按规定的( )定时地驱动( ),并保证气门有足够的( )和适当的( )。
【单选题】If you have a problem _____ your composition, you had better ask your teacher ______.
A.
in; on some advice
B.
for; for some advices
C.
on; some advice
D.
with; for some advice
【简答题】气门传动组的作用是按规定的( )定时地驱动( ),并保证气门有足够的( )和适当的( )。
【单选题】维生素C是一种重要的维生素，能防治坏血病，又称为抗坏血酸，其结构简式如图，下列有关它的叙述错误的是（ ）
A.
它的分子式为C 6 H 8 O 6
B.
易起氧化及加成反应
C.
它是一种水溶性维生素
D.
在碱性溶液中能稳定地存在
【多选题】Nowadays many documents are used in international cargo transportation，some of the documents can be transferred to the third parties and some can not be transferred to the third parties．Please point o...
A.
insurance policy can be transferred to the third parties
B.
insurance policy can not be transferred to the third parties
C.
sea waybill can be transferred to the third parties
D.
sea waybill can not be transferred to the third parties
【单选题】If you have some difficulties ____ your grammar, you had better ask your teacher ____.
A.
in; on some advice
B.
for; for some advices
C.
on; some advice
D.
with; for some advice
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