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 (ice) on lakes. It might be safe to
_______(skate) on lakes, but be very careful!
(although) it may feel cold, it might not be safe. The
(temperature) has to be at least
(minus) one or two
_______(degree) or even lower for several
(week) and the ice will be thick enough. Falling through the ice is
(dangerous). I am not
.(joke) You had better
_____(wear) kneecaps(护膝) .