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问题 选择题
已知二次曲线
x2
4
+
y2
m
=1，则当m∈[-2，-1]时，该曲线的离心率的取值范围是（　　）
A．[
2
，
3
]		B．[
5
，
6
]		C．[
5
2
，
6
2
]		D．[
3
2
，
6
2
]
答案

因为二次曲线

x2
4
+
y2
m
=1，m∈[-2，-1]，所以a=2，b2∈[1，2]，所以c2=a2+b2∈[5，6]，

所以双曲线的离心率e=

c
a
∈[
5
2
，
6
2
]；

故选C．

单项选择题

Calculator is (66) for performing arithmetic operations, but that requires human intervention to alter its stored program, if any, and to initiate each operation or sequence of operations. A calculator performs some of the functions of a computer, but usually operates only with frequent human intervention.

Microcomputer’s processing unit consists of one or more microprocessors, and includes storage and input-output (67) . Personal computer primarily intended for (68) use by an individual. (69) computer can be hand-carried for use in more than one location. Minicomputer is functionally intermediate between a microcomputer and a mainframe. And supercomputer has the highest processing speeds available at a given time for (70) scientific and engineering problems.

（66）处填（）。

A．suitable

B．well-formed

C．applicable

D．usable
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单项选择题

在直流电路中，电流流出的一端叫电源的（）。

A、正极

B、负极

C、端电压
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