A.border-left-radius:20px; B.border-top-left-radius:20px; C.border-radius-left-top:20px; D.border-radius-top-left:20px;
A.inline-block B.inline C.block D.none
A.width:0;height:0;border:10pxsolidtransparent;border-top-color:#00f; B.width:10px;height:10px;border:10pxsolid#00f;border-top-color:transparent; C.width:0;height:0;border:10pxsolidtransparent;border-bottom-color:#00f; D.width:10px;height:10px;border:0pxsolid#00f;border-bottom-width:10px;