【单选题】I delayed _______ your letter because I had been away for a week.
【单选题】I’m sorry I delayed_________ your letter because I have been quite busy these days.
【单选题】I delayed _______ your letter because I had been away for a week.
【单选题】“推荐分级的评价、制定与评估”( Grading of Recommendations Assessment, Development and Evaluation , GRADE )工作组那一年成立?( )
【单选题】I quickly answered your letter, for, if I delayed, you ______ I was not concerned about your difficulties.