單項選擇題門窗洞口砌筑時應(yīng)上下左右拉線找規(guī)矩,一般門框上皮應(yīng)低于門框過梁(),門框下皮應(yīng)比窗臺上皮高5mm。

A.10~20mm
B.5~10mm
C.10~15mm
D.10~25mm