In________, he began to learn Russian, when he was in________.[ ]

A. 1970; the 50's  

B. the 1970; his 50s

C. the 1970s; his fifties  

D. 1970s; his fifties

建设工程设计与施工采用总分包模式的特点有( )。

A．对总承包商要求高，业主选择范围小

B．总包合同价格可较早确定，合同金额较低

C．业主的合同结构简单，组织协调工作最小

D．分包单位多，简化了工程质量控制工作

E．工程设计与施工有机结合，有利于缩短建设工期