— I exercise three times a week.

1.John always does his homework____in order not to make any mistakes.
2.It's ____  to find any excuse when you do something wrong.
3.The factory makes a new type of cars which produces less air____.
4.All the victims were saved and taken to ____ .
5.We all know Mother’s Day is on the ____Sunday of May.            

木工师傅在做完门框后，为防止变形常常像图中所示那样钉上两条斜拉的木板条（即图中的AB和CD），这样做的根据是（　　）