A.1400mm B.1600mm C.1800mm D.2000mm
A.1 B.2 C.3 D.4
A.偏斜37°上斜裂紋 B.偏斜37°下斜裂紋 C.偏斜53°的上斜裂紋和水平裂紋 D.下斜裂紋和水平裂紋