防止钢铁的腐蚀是世界级难题，每年全世界钢产量的四分之一因腐蚀而损失

用所给词的适当形式填空

My watch doesn’t work. It needs to ____ .
Who ____   away my pen? I can’t find it.
Lucy said she____ the primary school the next month.
 It’s correct____  strangers come into your house.
 It’s ____ to join a charity walk than to play computer games.