题目内容：

词形转换（本题有10小题，每小题1分，共10分）

When it is very, very cold, there’s 1.     (ice) on lakes. It might be safe to          2._______(skate) on lakes, but be very careful! 3.     (although) it may feel cold, it might not be safe. The 4.        (temperature) has to be at least 5.      (minus) one or two 6._______(degree) or even lower for several7.    (week) and the ice will be thick enough. Falling through the ice is8.     （dangerous）. I am not 9.     .(joke) You had better10._____(wear) kneecaps(护膝) .