Seven-string guitars have an extra low string which is a B in standard tuning.

七弦琴有一根特低弦，在标准调弦里是B音。

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Because of low yield, saponin B was not identified.

皂甙b因得率极低，未能完成鉴定。

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Because of low yield, saponin B was not identified.

皂甙b因得率极低，未能完成鉴定。

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