微机继电保护测试:had been done与had done的区别，何时选前者，何时选后者？

had been done与had done的区别，何时选前者，何时选后者？ had been done与had done是什么结构 他们的用法是什么 had+done 与have+done有什么区别? HAD BEEN TO They had done that before 请教had been 的用法 从句you had been gone have been与had been的区别？（谢瓜了） The bill he had long been opposed_____...... had been是怎么用的?谢谢!