A.≤300mm、≥200mm B.≤200mm、≥300mm C.≥300mm、≤200mm D.≥200mm、≤300mm
A.6 B.9 C.10 D.12
A.自拱頂向兩邊對(duì)稱反向 B.自兩邊拱腳對(duì)稱地相向 C.兩側(cè)分別自拱頂和拱腳相向 D.兩側(cè)分別從腰部向拱頂和拱腳反向