题目如图,已知等边△ABC\triangle ABC△ABC的边长为aaa,中线BD=bBD=bBD=b,点EEE在BDBDBD上,连接AEAEAE,在AEAEAE的右侧作等边△AEF\triangle AEF△AEF,连接DFDFDF,则△ADF\triangle ADF△ADF周长的最小值是( )A.12a+b\frac{1}{2}a+b21a+bB.a+ba+ba+bC.a+12ba+\frac{1}{2}ba+21bD.12a+12b\frac{1}{2}a+\frac{1}{2}b21a+21b知识点:三角形综合题章节:未标注