Question

英语语法问题 after having...

After having learned the distinct characters of SARS's infection , residents in this zone made a brilliant achievement in preventing SARS.
句中 having的语法作用是什么?为什么加ing

Answer 1

After having learned the distinct characters of SARS's infection, residents in this zone made a brilliant achievement in preventing SARS.

1. After 是介词，后面接动词ing形式

2. have done 表示 现在完成时

整句话的意思是：在知道“非典”的感染区域特性后，在这个区域的居民们在预防“非典”方面取得了辉煌的成就。

Answer 2

have作为助动词，构成完成时时态。这句话可以看作是下面时间状语从句的省略：
After they had learned the distinct...
把从句主语they省略之后，had learned要由谓语动词变为非谓语，修饰residents，两者间的关系是主动，所以用having learned。