城市送电网中一次送电网一般以( )方式结送为宜。
A．放射式
B．环式
C．联络线
D．多回线式
参考答案：B
（）又分为生物辅助能和工业辅助能。
A.自然辅助能
B.人工辅助能
C.有机能
D.无机能
With the improvement of people's living conditions, most mothers _______ in hospitals. [ ]
A. have delivered their babies
B. have born their babies
C. have their babies born
D. have their babies delivered
