though引导的虚拟从句,5个例句,动词的使用方法

though引导的虚拟从句,5个例句,动词的使用方法
以下句子从句的动词该怎么分析呢?
1.Mike seemed very proud of himself as though he were the only person who scored over 90.(为什么是he were?)
2.Mary left the old house in a hurry ,looking frightened as though she had seen a ghost there.(为什么是she had seen?)
3.The old lady gave all that she had to the young man,treating him as though he were her own son.（为什么是he were?）
4.Tom dressed himself so formally today,as though he were attending a party.（为什么是he were attending?）
5.He always boasts of his rich experience as though he knew everything.(为什么是he knew?)