the boy's not having done his homework 是名詞短語,在句子裏做主語
2. On hearing the news(非常正式,口語裏不用)= When he heard the news(口語、書面語都可用)
3. 有先後關系
4. 過去式: I would rather you didn't do anything for the time being. 我寧願妳暫時先不要采取什麽措施.