【名词&注释】
粉煤灰砖(fly ash brick)、烧结多孔砖(fired perforated brick)、烧结空心砖(sintered hollow block)、实心砖(solid brick)
[单选题]边长在800mm以下的柱的截面模数为()
A. 50mm B. 100mm C. 25mm D. 200mm