如图，老师用同样的力气吹一根吸管，并将它不断剪短．这是为了研

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问题选择题

如图，老师用同样的力气吹一根吸管，并将它不断剪短．这是为了研究声音的（　　）

A．响度与吸管长短的关系

B．音色与吸管材料的关系

C．音色与吸管长短的关系

D．音调与吸管长短的关系

答案

答案：D

选择题

Atlanta ____ a series of fierce fights between blacks and whites in the 1960s. [ ]

A. met

B. saw

C. happened

D. made

选择题

—Did you catch the early bus this morning?

—No. It had left the stop ________ I arrived there.[ ]

A. as soon as

B. as the time

C. by the time

D. during the time