直接用過去分詞開頭作狀語時不強調(diào)動作的時間,盡管這一動作有時也發(fā)生在謂語動詞之前.只強調(diào)被動.如:Led by the Party,we have achieved great success.在黨的領(lǐng)導下,我們?nèi)〉昧司薮蟮某晒?
又如:Respected by the students,the teacher is very happy.受到學生們的尊重,老師很高興.
當用Having +過去分詞時,主要強調(diào)動作發(fā)生的時間是在謂語動詞之前.
如:Having finished his homework,he went out to play with his friends.做完作業(yè)之后,他出去和朋友玩了.
至于找主語的問題,你只要知道主語是謂語動作的發(fā)出者,沒有謂語動詞的動作哪有什么主語,省掉是省掉的問題.這和非謂語動詞不是一碼事.