A.br B.input C.img D.form
A.background-image B.background-repeat C.background-width D.background-attachment
div1里依次有div2和div3兩個(gè)同級(jí)元素, div2高20px,margin-bottom:30px; div3高50px,margin-top:20px; 那么div1的高度是多少?()
A.120px B.100px C.70px D.90px