壁纸的可洗性按使用要求分可洗、可刷洗、特别可洗3个等级，根据《聚氯乙烯壁纸》，特别可洗壁纸可以洗多少次而外观上无损伤和变化？( )

A．high oil production rate,  not easy to repair
B．high gas production rate,   easy to repair
C．low oil production rate,  not easy to repair
D．low gas production rate,   easy to repair

A.钢材
B.钢筋混凝土
C.花岗岩
D.普通砖