all alone 单独、独自
【例句】
She was sitting all alone in the classroom. 她独自一人坐在教室里。
There being no one to help me, I had to do it all alone. 因为没有人帮助我，我不得不独立完成这项任务。
【Question 提问】
句型转换
She was sitting all alone in the classroom.（保持句意不变）
She was sitting all by ______ in the classroom.
答案：herself