A.0.3m B.0.4m C.0.5m D.0.6m
A.上端應(yīng)用繩子綁牢 B.中部應(yīng)用繩子綁牢 C.下端應(yīng)用繩子綁牢 D.無(wú)需綁扎
A.1 B.2 C.3 D.4