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【简答题】
（7）文昌鱼等原索动物为适应其被动取食方式，咽部___，在咽部腹面正中具有___，背正中具有___。
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【简答题】阅读理解。 Everyone has got two personalities - the one that is shown to the world and the other that is secret and real．You don't show your secret personality when you're awake because you can control you...
【简答题】阅读理解。 Everyone has got two personalities (性格) -the one that is shown to the world and the other that is secret and real. You don't show your secret personality when you're awake because you can contro...
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【单选题】设有关系 R 和 S ,在下列的关系运算中,( )运算不要求 R 和 S 具有相同的目数,也不要求对应属性的数据类型相同。
A.
R ∪ S
B.
R ∩ S
C.
R-S
D.
R × S
【简答题】任务型阅读.。 Everyone has got two personalities: one is shown to the world and the other is secret and real . You don’t show your secret personality when you are awake , but when you are asleep, your slee...
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【单选题】设有关系 R 和 S ,在下列的关系运算中,( )运算不要求 R 和 S 具有相同的目数,也不要求对应属性的数据类型相同。
A.
R ∪ S
B.
R ∩ S
C.
R-S
D.
R × S
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