读图中四幅气温曲线图，完成填空．
There are ____ (three/there) swings.
将木材隔绝空气加强热，可得到木煤气、木焦油和木炭等，这种加工方法化工生产中称为（ ）
More historical buildings in the old town will fall down________we try our best to protect them.
