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问题 不定项选择
不定项选择
关于波长的下列说法中正确的是（   ）
A．机械振动在一个周期内传播的距离就是一个波长

B．在波形图上位移相同的相邻两质点之间的距离等于一个波长

C．在波形图上速度最大且相同的相邻两质点间的距离等于一个波长

D．在波形图上振动情况总是相同的两点间的距离等于一个波长

答案

答案：A

选择题

— I’m afraid I can only make a small contribution this time.

—____.We really appreciate your assistance.

A．The best things come in small packages

B．The more,the better

C．It is better to give than to receive

D．Every little helps
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选择题

Do you know whom this bird _____? [ ]

A. belong to

B. belongs to

C. is belonged to

D. is belonging to

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