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【单选题】
设p={(A1，A2)，(A1，A3))是关系R(A1，A2，A3)上的一个分解，表8-3是R上的一个关系实例r，R的函数依赖集为(52)，分解p(53)。A.
F={A1→A2，A1→A3}
B.
F={A1→A2}
C.
F={A1→A3}
D.
F={A1A3→A2，A1A2→A3}
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【单选题】I have called the station and they told me the next train for Chongqing _____at 2:30.
A.
will leave
B.
left
C.
has left
D.
leaves
【多选题】在下列叙述中那些是正确的?
A.
对于全同粒子体系，变换其中任何一对粒子都不改变体系的状态
B.
全同电子体系的波函数对于任何两电子的交换是对称的
C.
全同电子体系的波函数一定可以写成空间部分与自旋部分之积
D.
全同粒子体系的波函数永远具有确定的交换对称性
【多选题】下列有关RNA的叙述那些是正确的
A.
RNA分子也有双螺旋结构
B.
tRNA是分子量最小的RNA
C.
RNA不一定要形成高级结构才发挥其活性
D.
rRNA参与核糖体的组成
E.
mRNA是合成多肽链的直接模板
【简答题】One day Mrs.Wilson went shopping with Tracy and Ben.They went to the supermarket in the new shopping center. “Why do you buy things here ? ” Tracy wanted to know.“Because they are cheaper here than at...
【简答题】At some point I noticed that people were staring at me. The box boys at the supermarket spoke to me with respect. People were mistaking me for somebody else. It had to be somebody who weighed close to...
【单选题】They told me they had just arrived at the last destination ________ you went to last year.
A.
where
B.
that
C.
when
D.
which
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