Many college graduates are willing to start online shops to get over the period ______ they have difficulty finding a satisfactory job.

A．where

B．when

C．which

D．that

己知某5层商店住宅进深6m，开间3.3m，其局部平剖面及楼(屋)盖恒载和活载如题图所示。托粱b×h_b=250mm×600mm，混凝土为C30，纵筋为HRB335级，箍筋为 HPB235级；墙体厚度240mm，采用MU10烧结多孔砖，计算高度范围内为M10混合砂浆，其余为M5混合砂浆；顶梁，b_t×h_t=240mm×180mm托粱自重为4.185kN/m，每层墙体自重为11.59kN/m。

墙梁跨中截面的计算高度为下列（）项数值

A．2.96m

B．2.90m

C．2.66m

D．11.6m