Question

合并成主从复合句.She runs fad.her sister runs vevy fast

Answer 1

She runs fast while her sister runs very fast.

She runs fast but her sister runs very fast.

这两句话似乎很难搞成主从复合句.上两句是并列句.

可用定语从句试一下.

She runs fast,whose sister runs very fast.(似乎意思有点怪）