had been puzzled over the problem for over an hour without any resultI had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.A whileB whenC then D as 应该选B.为什么?各个

had been puzzled over the problem for over an hour without any resultI had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.A whileB whenC then D as 应该选B.为什么?各个 had been what had been done had been done. so the man had puzzled look on his face 这句话最准确的意思是什么 where had she been? had been什么时态 英语翻译had been reading have been talking, had been told? 英语,has been和 had been Had been telling和 Had told 求问had gone和had been had been doing 和had been done有什么差别 had been doing 和had been done有什么差别? he had been reduced.he had been reduced 啥意思 had been和had been to的区别 什么时候用had been in什么时候用had been to? had been doing 是什么时态? If there had not been 改成 had not there been 是had not there been 还是had there not been?