答案：1. problems
解析：根据Celia写给Scott的信中“These things always happen and she doesn't care about my feelings. I need your help.”可知，这些是Celia和Lana之间的问题，“问题”用problems表示，此处用复数形式，故填problems。
2. drops
解析：由Celia信中“After she eats it, she drops the litter into my desk.”可知，她把垃圾扔进“我”的书桌，主语是She，时态是一般现在时，谓语动词用第三人称单数形式drops，故填drops。
3. return
解析：根据“After she borrows my pencil, she doesn't return it.”可知，她不归还铅笔，doesn't后接动词原形return，故填return。
4. copies
解析：从“I get angry when she copies my homework.”可知，她抄袭“我”的作业，主语She是第三人称单数，谓语动词用copies，故填copies。
5. clothes
解析：由“And she sometimes makes ink marks on my clothes with her pen.”可知，是在“我”的衣服上弄上墨迹，故填clothes。
6. solutions
解析：Scott的回信中提到Lana想要改变，并列举了一些对应的解决办法，所以可填“solutions”。
7. bag
解析：根据“She agreed to put the litter in a bag.”可知，她会把垃圾放进袋子里，故填bag。
8. mind
解析：由“She asked you to remind her by saying 'Would you mind returning my pencil?'”可知，此处填mind，故填mind。
9. myself
解析：从“She said she would do her own homework”可知，她会自己做作业，“独自”用by myself，故填myself。
10. careful
解析：根据“be careful with her pen”可知，她会小心使用钢笔，故填careful。|