When they said goodbye to each other __(5) __ the end of the vacation, they promised that they __(6)__ in touch by mailing.Đoạn văn27/33When they said goodbye to each other __(5) __ the end of the vacation, they promised that they __(6)__ in touch by mailing.keptwould keepwill keephave keptGiải thíchChọn đáp án B