I don’t think his success has a lot to do with good luck. It’s hard work ______ has made him what he is today.

A．which

B．that

C．where

D．why

某公路工程场地为松散粉细砂场地，场地土层最大孔隙比为0.98，最小孔隙比为0.67，天然孔隙比为0.92，采用砂桩处理，按正三角形布桩，要求处理后土的相对密度达到0.85，砂桩直径为40cm，按规范JTGD63-2007计算。

垫层底面处自重应力值Pcz为（）。

A.28.5kPa

B.30kPa

C.66.0kPa

D.66.5kPa