1 . 用所给短语的正确形式填空，注意：有两个短语是多余的。

ahead of schedule;   stick out;   sign up for;   look forward to;   be responsible for;   in a flash;   take notes;    in exchange for;   concentrate on;   make an impression on;   be anxious about;   decide on

1. We have a ten-day holiday. Let's __________ the date when we are going camping.
2. The dog is standing there and it is __________ its tongue.
3. The man was out of the back door and disappeared __________.
4. My mother __________ the safety when I studied abroad.
5. We finished the project three weeks __________.
6. He gave me some milk __________ some food in the town.
7. The unique tea culture __________ the foreign students at the meeting.
8. __________ the lesson was extremely hard because the room was noisy.
9. I am __________ hearing from you.
10. He sat there to __________ of everything that was said.

5 . The questions raised by the math teacher were so difficult that I ________ on the first one. (stick)
数学老师提的问题太难，第一个我就答不上来。