根据下列句子所给汉语注释或单词首字母，写出空缺处各单词的正确形式。（每空只写一词）
1. Mr. Liu, our English teacher, explained the s__________ of the themes expressed in the poem with passion.
2. As the price of houses are getting higher and higher, most young people choose to rent a f______ flat.
3. Please accept my c________ on your graduation..
