had been doing是什么语法?举个例子~有have/has been doing的说法吗?

had been doing是什么语法?举个例子~有have/has been doing的说法吗? had been doing 是什么时态? had been doing是什么时态 had been doing是什么时态 had been doing是什么是时态? have been doing,had been doing,will have been down是什么 you been fighting?为什么是been doing?看图!这是什么语法?有been doing这个搭配? had been doing 和had been done有什么差别 had been doing 和had been done有什么差别? had been doing是主动还是被动 新概念英语里面这段话是什么语法啊?新概念第三册第二课,“i have been coming up he night after night”,have been doing 是什么语法啊? 英语时态区分have done .have been doing.had done.had been doing.有什么区别. had been doing 和 had done的区别 i soon found that the work i was doing had akready been done by someone else. that后面是什么从句?i was doing 又是什么成分? had been doing是什么时态,从过去持续的现在?还是过去的过去?还是别的什么 had been looking forward后面加to do 还是doing? He sent another fax informing Tom that the plan had been called off.请问这里的informing是什么语法现象. 请分析这句英语的语法The cave might never have been discovered had not the entrance been spotted by the distinguished French potholer,Berger请分析这句话的语法,中文意思我知道,关键是什么语法结构.