— _________________

— She is singing. [ ]

A. What are they doing?

B. What's she doing?

C. She is laughing.

由桩径d=800mm的灌注桩组成的群桩，纵横向桩距S_ay=S_ax=3d，因大面积填土引起桩周土出现负摩阻力，中性点以上桩周土层厚度加权平均负摩阻力标准值=16kPa，γ_m=10kN/m³。按《建筑桩基技术规范》(JGJ94-2008)规定，负摩阻力桩群桩效应系数η_n实际上取( )。

A．1.27

B．1

C．0.78

D．0.56