参考答案：D

解析：appreciation“感激；评定；鉴赏”，如：She showed little or no appreciation of good music．她对于好音乐毫无鉴赏的能力。We take this opportunity to express our sincere appreciation of your help．借此机会我们对你们的帮助表示衷心的感谢。此词显然不合题意。assurance“保证；把握；信心”，如：“She'll like that book，”said John with assurance．“她会喜欢那本书的，”约翰有把握地说。assumption“假定，设想”，如：Their assumption that the war would end quickly was proved wrong．他们认为战事会迅速结束的看法是错误的。assessment“估价；评价”，如：a correct assessment of historical figures“对历史人物的正确评价”。所以正确答案应为D。