分类：教育/科学-外语学习-英语考试
问题：请帮忙告知答案并写明为什么，非常感激！！！1、Wehaverec 
1、We have receiv your enquiry of 15 October _____ you advise us of your interest in Cashmerea、in which      b、at whichc、at which      d、from which2、 We have received your letter of September 12, ______ we are glad to know that you are interested in our electric heaters1、We have receiv your enquiry of 15 October _____ you advise us of your interest in Cashmerea、in which      b、at whichc、at which      d、from which2、 We have received your letter of September 12, ______ we are glad to know that you are interested in our electric heatersa.which        b.at whichc.in which     d.from which 
回答：1.a 这是限制性定语从句。翻译是：在信里你邀请我们……
2.d 这是非限制性定语从句。翻译是：从这封信我们很高兴知道……