如图,正方形ABCD中,对角线AC、BD交于点O,将BD绕点B逆时针旋转30°到BE所在的位置,BE与AD交于点F,分别连接DE、CE.
—I think students should have mobile phones to call their parents.
— . They often use them to play games instead.
冷饮店中A饮料与B饮料共有280箱,它们的数量比是3∶4,那么B饮料有____箱.
有X、Y、Z三种金属,把Y投入X(NO3)2溶液中,Y表面有X析出;把X投入Z(NO3)2溶液中,X表面有Z析出。X、Y、Z三种金属的活动性由强到弱的顺序是( )