A.8~10m B.10~20m C.20~30m D.30~40m
A.15m B.20m C.25m D.30m
A.Sa2≤0.2Ri+0.1h B.Sa2≥0.2Ri+0.1(h+A/) C.Sa2≥β'[0.2Ri+0.1(h+A/)] D.Sa2≥0.3β'Ri