A.10°~12° B.10°以下 C.10°~15° D.15°以上
A.先墻后拱、自上而下 B.先拱后墻、自下而上 C.先墻后拱、自下而上 D.先拱后墻、自上而下
A.1/4~1/2 B.1/2~1/3 C.1/4~1/3 D.1/3~2/3