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问题 单项选择题

WG-21A型无绝缘轨道电路自动闭塞（“N+1”系统），ZW•XK1空芯线圈的电感（）。

A、33.5μH±1μH

B、30.0μH±2μH

C、35.5μH±1μH

D、35.5μH±2μH

答案

参考答案：A

选择题

已知四棱锥的侧棱都相等，那么四棱锥的底面（　　）

A．存在外接圆

B．存在内切圆

C．为正方形

D．为矩形
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改错题

短文改错。

Last winter vacation,some of my classmates decide to

                                                            1._________

travel with their friends, while I chose to take part-time

job                                                        2._________

to gain experience and earn some money. I learn from

my                                                         3._________

teacher that a nearby company was looking after students

                                                             4.__________

with good handwriting to write addresses on envelope. The

                                                              5._________

pay were 10 cents per envelope. I headed for the company,

                                                             6.__________

feeling sure l would easy finish 300 envelopes in five hours

and                                                       7._________

to earn the money. Actually,I only finished 200. Now, I

                                                             8.__________

fully understand how hard is to earn money. Getting out

                                                             9.__________

of the classroom is indeed necessary for we all.

                                                              10._________
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