Has existed是现在完成时
Had existed是过去完成时,表示过去的过去.如这句话,I had been there for a long time before you arived.你到达那已经是过去时,我比你先到达,是过去的过去,即过去完成时.
Has existed是现在完成时
Had existed是过去完成时,表示过去的过去.如这句话,I had been there for a long time before you arived.你到达那已经是过去时,我比你先到达,是过去的过去,即过去完成时.