句型转换
因为had done”中的was/were是助动词，所以在进行句型转换中要注意不需要再另外借助助动词do/did/does，而是直接借用had。如：
肯定句：He had worked here for a good many years. （他在这里工作了很多年了。）
否定句：He hadn't worked here for a good many years.
一般疑问句：Had he worked here for a good many years?
特殊疑问句：How long had he worked here? （划线部分为a good many years）
