5. __________ struck, a tuning fork produces an almost pure tone, retaining its pitch over a long period of time.
(A) When is it
(B) One is
(C) When it is
(D) Is one
看不懂句子的意思,想知道
当被敲击,一个音叉发出一种近乎于纯的声音,这个音的音高保持很长一段时间。
谢谢了
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