楼梯踏步的坡度在以下列（)组较合适I.15°Ⅱ.30°Ⅲ.50°Ⅳ60°Ⅴ70°Ⅵ80°A.I、ⅡB.Ⅲ、ⅣC.V、ⅥD.Ⅱ、Ⅵ

楼梯踏步的坡度在以下列()组较合适I.15°Ⅱ.30°Ⅲ.50°Ⅳ60°Ⅴ70°Ⅵ80°

A.I、Ⅱ

B.Ⅲ、Ⅳ

C.V、Ⅵ

D.Ⅱ、Ⅵ