11.  It was difficult for me to learn English.

12.  Forget all these things what you had done are to be answered for !

13.  The chemical lab is very bad for us to have a lesson.

14.  Now we will say good-bye to the lab and we know a quite condition is very important for us to have lessons.

15.  I thank Miss, you make me know that some things are one of my business, so it is not necessary for me to speak at great length on some questions .

16.  So it is difficult for us to pass.

17.  Though it is difficult for us to do that .

18.  Though it is difficult for me to do that, and I have no confidence for it, I can try my best to do it well.

19.  It is important for us to do it well.

20.  Dear Sweet: I'm sorry to write the letter for your so late .