单项选择题
A.钢钉 B.膨胀螺栓 C.发泡胶 D.射钉
A.10 B.15 C.20 D.25
A.1:3;2m;50mm B.1:2;2m;50mm C.1:3;1.8m;50mm D.1:2;2m;40mm