①△BDF和△CEF都是等腰三角形;②DE=BD+CE;③△ADE的周长等于AB与AC的和;④BF=CF.其中正确的有____.(填正确的序号)
Han Han's books are popular. They __________ by many teenagers.
X、Y、Z、M四种金属,已知X可以从Y的盐溶液中置换出Y:X和Z作原电池电极时,Z为正极;Y和Z的离子共存于电解液中,Y离子先放电;M的离子的氧化性强于Y的离子.则这四种金属的活动性由强到弱的顺序为( )
下列物质中,属于氧化物的是()
— Much ________. I think I can go to school tomorrow.