In the seventeenth century the organ, the clavichord，and the harpsichord became the chief instruments of the keyboard group，a supremacy they maintained until the piano supplanted them at the end of the eighteenth century.
(同位语a supremacy)
17世纪时风琴、敲弦琴和拨弦琴成为键盘乐器类的主要成员，这种至高无上的地位一直由它们保持，直到18世纪末被钢琴所取代。
分句1：In the seventeenth century the organ, the clavichord，and the harpsichord became the chief instruments of the keyboard group.
分句2：a supremacy they maintained until the piano supplanted them at the end of the eighteenth century.
分句2是分句1的同位语从句，用来修饰说明分句1中的the chief instruments of the keyboard group.
版权声明：本文系网独家稿件，版权为网所有。转载须注明来源及作者，否则必将追究法律责任。
微信扫描下方二维码，第一时间知晓托福考试真题预测及解析，还有北美留学最新动态喔~(微信号：toefl120)!