根据下列句子及所给单词的首字母，写出各单词的完全形式。 1. Take two of the pills three times d______ before meals. 2. The d______ of a friend is always sad. 3. I think he will work out the problem, because he is quite a p______ person. 4. Food and water are n______ to man. We can't live without them. 5. If you want to get a good result in the exam, you must pay a______ to what your teacher says in class. 6. It's our d______ to clean up the city parks so that our city looks more beautiful. 7. Marie and I are good friends and we think our f______ will last forever. 8. My bike was l______. I have to buy a new one. 9. By the end of last t______, we had learned more than 2,000 words. 10. I won't go to the party u______ I am invited.