题目内容：

When it’s very cold，it might be safe 1. (skate) on lakes, but be very 2.(careful)! Although it3.(may) feel cold, it might not 4.(safe). The temperature 5. (have) to be at least minus one 6.(连词) two 7.(degree) or even colder 8. (介词) several weeks. Falling through the ice is 9.(dangerous). I am not 10.(joke)!