当状语从句中的动作发生的时间早于主句的动作, 分词短语可用having+ 过去分词完成形式,(一般用于时间和原因), 但注意下例动词可不用以上结构. (know, hear, see, arrive, learn等) Not knowing where he was, I had to go alone. Learning that he won't come, I don't what to do. Hearing the sad news, I felt disappointed. Arriving at the station, I found the last train gone. 6. 为了便于理解, 有些连词可仍然放在分词短语的前面. 1. While going to school, I met my former classmate. 2. Once seen, it won't be forgotten. 3. Though tired, he is still in high spirits. 4. If heated, the metal expands. 6. If playing all day, you will waste your valuable ...