He was so busy that he couldn't go to the concert.（改成同义句)
问题描述：
He was so busy that he couldn't go to the concert.（改成同义句)
顺便提一下：Rose knows something about the matter.（改为否定句）
He is an American child.(改为复数形式)
He was so busy that he couldn't go to the concert.（改成同义句)He was_________busy____________go to the concert.
答
He couldn't go to the concert as he was so busy.
Rose doesn't know anything about the matter.
They are American children.