A.5~8 B.8~10 C.10~16 D.16~20
A.傳力明確 B.穩(wěn)定性好 C.抗風(fēng)能力好 D.耐久性好
A.1~1.1 B.1.1~1.3 C.1.2~1.4 D.1.5~2