单项选择题
A.50mm B.60mm C.70mm D.100mm
A.平行屋脊 B.垂直屋脊 C.中间平行屋脊,靠墙处垂直屋脊 D.靠墙处平行屋脊,中间垂直屋脊
A.7d B.10d C.14d D.21d