单项选择题
A.双层公路桥面钢桁架梁B.公铁两用双层流线型闭合式桁架箱梁C.单层桥面钢桁架梁D.公铁两用的双层桥面钢桁架梁
A.360cmB.600cmC.752cmD.1000cm
A.469cmB.415cmC.909cmD.265cm