题干
My _________ sister explained _________ me why she used my bike.
A：older, for
B：older, in
C：elder; to
D：elder; for
答案(点此获取答案解析）
C
My _________ sister explained _________ me why she used my bike.
A：older, for
B：older, in
C：elder; to
D：elder; for
，则椭圆的方程为
