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问题 选择题
椭圆x2+2y2=6的离心率为（　　）
A．
2
B．
2
2
C．
1
2
D．
3
3
答案

∵x2+2y2=6，∴

x2
6
+
y2
3
=1，

∴椭圆x2+2y2=6的离心率e=

c
a
=
6-3
6
=
2
2
．

故选B．

单项选择题

维生素A与三氯化锑的呈色反应，其生成物的颜色为

A．蓝色
B．紫红色
C．蓝色渐变成紫红色
D．黄色
E．黄色变成桃红色
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单项选择题

All of the following are benefits of derivatives markets EXCEPT:()

A. transactions costs are usually smaller in derivatives markets, than for similar trades in the underlying asset. 

B. derivatives markets help keep interest rates down and supply valuable price information. 

C. derivatives allow the shifting of risk to those who can most efficiently bear it.
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