I didn't know she could swim 中为什么用could

I didn't know she could swim 中为什么用could i didn't know how i could do things for myself before.从句中事态不 She didn't know how she could get to the railway station.（同义 the little girl didn't know how she could get home.改为同义句 Mike didn't know what she could da for her mother.(改为简单句） Acice didn't know how she could draw horses well.(写出同义句) He Alice didn't know how she could draw horses well.(改为同义句） Alixe didn't know how she could draw horses well.(改为简单句) I always wanted to forget you,but I didn t know I could only i didn't know this was something i could do until i got my r I didn't know what could I said这句有错么 I could not see anything and I didn’t know if _____________