如图,△ABC≌△DCB,A、B的对应顶点分别为点D、C,如果AB=7cm,BC=12cm,AC=9cm,DO=2cm,那么OC的长是 ____cm.
①资本主义社会的基本矛盾激化
②实行“自由放任”政策
③贫富悬殊
④狂热的股票投机
The Chinese saying “A tree can't make a forest” tell us that is very important in a football match.
下列描述中,属于我国北方地区地理环境特征的是( )