piano is her main focus she's also great at guitar．A. SinceB. OnceC. UnlessD. While

问题补充：

．piano is her main focus，shes also great at guitar．

A. Since

B. Once

C. Unless

D. While

答案：

A. Since

B. Once

C. Unless

(答案→)D. While

解析：考查状语从句的连词。While=though尽管；句意：尽管钢琴是她的主要学习的乐器，她还很精通吉他。