下列关于声音的产生和传播叙述正确的是_刷题宝

题干

下列关于声音的产生和传播叙述正确的是（）

A：吹笛子，笛管振动发声

B：空气中的光速大于声速

C：扬声器发声不需要振动

D：超声波可在真空中传播

上一题下一题 0.0难度选择题更新时间:2016-09-08 06:43:52

答案(点此获取答案解析）

B

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Free Activities This Weekend
An Open-air Craft(工艺)Market in Front of the City Hall Sunday from8:30A.M. to 6:30 P.M. Need to buy a present? Find bamboo toys, paper flowers, paper umbrellas, model cars and more! Food from around the world, too!	City Museum Travel Movies Meeting Room Sat.& Sun. at 2:30 P.M. Do you want to travel but don't have enough money? See movies on Japan, Italy, America, England, Russia, and Australia. There are only 80 seats, so come early.	Autumn Fashion Show Golden Shopping Center Sunday at 3:00 P.M. Men's and women's autumn clothes. See 25 handsome and pretty models show the latest fashions. All clothing will be on sale after the show for under ￥100.
Pop Concert at Yunhai Square Saturday from 9:00 P.M. to midnight Five groups of college students are going to play the guitar and sing pop songs. Bring your own food and drink.	Library Lecture(讲座) City Library Hall Saturday at 10:00 A.M. How to find the job that you really want! Two-hour lecture. Advice on choosing and getting the right job for you. Coke and sandwiches are sold.

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