Peter, as well as his two sisters Sondra and Emily, ____ left-handed.

A．is

B．has

C．are

D．have

某天然稳定土坡，坡角35°，坡高5.0m，坡体土质均匀，无地下水，土的e和Ι_L均小于0.85，γ=18kN/m³，f_ak=160kPa，坡顶部位拟建工业厂房，采用条基，作用基础顶面竖向力F_k=350kN/m，基础宽度2.0m，按厂区整体规划，基础底面边缘距坡顶4m。试问条基的埋深应多少才能满足要求。