A:will it be until
B:it will be before
C:will it be whe
D:it will be that
①酸性:HClO4>HBrO4>HIO4
②离子还原性:S2﹣>Cl﹣>Br﹣>I﹣
③沸点:HF>HCl>HBr>HI
④金属性:K>Na>Mg>Al
⑤气态氢化物稳定性:HF>HCl>H2S
⑥半径:O2﹣>Na+>Na>Cl.
求抛物线y=2x2﹣3x+1的顶点和对称轴.