根据所给音标及释义写出单词。
1. _____ [] a small piece of paper that one sticks on an envelope (信封)
2. _____ [] keep something for a later time
3. _____ [] especially (特别的)
4. _____ [] the most important city of a country or state
5. _____ [] a person from another country
6. _____ [] sure; not doubtful (可疑的)