在抗日战争中,八路军为了伏击日军火车,侦察员常用耳朵贴着铁轨来提前判断是否来了火

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问题:

在抗日战争中,八路军为了伏击日军火车,侦察员常用耳朵贴着铁轨来提前判断是否来了火车.这是利用声音在铁轨中的传播速度______声音在空气中的传播速度.(填“大于”“小于”或“等于”)

考点:声速
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时下社会流行着这样的顺口溜:“读书苦读书累、读书还要交学费、不如参加黑社会,有吃有喝有地位” 你认为顺口溜说得有道理吗? 

                                                                                                                                                               

                                                                                                                                                               

                                                                                                                                                               

                                                                                                                                                                

                                                                                                                                                                

                                                                                                                                                                

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She doesn't know anyone here. She has got ______ to talk to.[ ]

A. anyone

B. someone

C. everyone

D. no one

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《瞎子阿炳全集》于()年出版.

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一般性重组包括DNA片段的物理交换,该过程涉及DNA骨架上磷酸二酯键的断裂和重新形成。( )

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眼睑的皮肤层具以下几个特点,除了()

A.薄而疏松

B.富有弹性

C.多皱褶

D.易移动

E.易伸展

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