语音等级路线 Voice-Grade Line
语音等级
Speech grade
以上为机器翻译结果，长、整句建议使用 人工翻译 。
《语音篇》为基础阶段辅助教材，其余三篇主干教材依次按基础、初级、中级三个等级设置。
The Phonetics book is a supplementary one at the starter's level, while the other three are designed for learners at starter's, elementary and intermediate levels respectively.
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