They have been collecting shells for there years.（改为同义句）
问题描述：
They have been collecting shells for there years.（改为同义句）
Has Tom been skating for hours?(做否定回答）
My mother has been collecting stamps for about ten years.(向画线句子提问）
答
1.They have been collecting shells since three years ago.
2.No,he hasn't.
3.What has your mother been collecting for about ten years?
不明白的再问哟,请及时采纳,多谢!