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【单选题】
在本节中，我们学过了如何将中缀表达式转化为逆波兰表达式，那么反过来，思考一下如何将逆波兰表达式还原为中缀表达式呢？试将下列逆波兰表达式还原为中缀表达式：1 2 + 3 4 ^ *A.
(1-2)*3^4
B.
(1+2)*3^4
C.
(1+2)^3*4
D.
(1+3)*2^4
参考答案：
参考解析：
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A.
The property of a B-tree is violated due to removing a key 删除关键码后违反了B树的性质
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The property of a B-tree is violated due to inserting a key 插入新的关键码后违反了B树的性质
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A B-tree becomes too high B树的高度过高
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$\frac{1}{3\sqrt{y}}$
B.
$\frac{1}{\sqrt{y}}$
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$\frac{1}{2\sqrt{y}}$
D.
$\frac{1}{4\sqrt{y}}$
【单选题】Which consequence follows as a B-tree becomes higher?B树高度的增加一定伴随着：
A.
Each node has a larger number of keys 每个节点所存放的关键码数量增加
B.
Each node has a smaller number of keys 每个节点所存放的关键码数量减少
C.
Splitting to the root 分裂到根
D.
Splitting to the leaves 分裂到叶
【单选题】令$f(x)=\frac{x^{2}}{1+x^{2}}$,则它的不定积分为（）
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x-arccotx+c
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x-arccosx+c
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x-arcsinx+c
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x-arctanx+c
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