支撑桁架的斜杆aB采用单角钢截面，最适合的截面形式为下列何项？A.1L45×4,A＝3.49cm,i＝0.89cm,i＝1.38cmB.1L50×3,

1.[不定向选择题]支撑桁架的斜杆aB采用单角钢截面，最适合的截面形式为下列何项？A.1L45×4,A＝3.49cm,i＝0.89cm,i＝1.38cm B.1L50×3,A＝2.27cm,i＝1.0cm,i＝1.55cm C.1L63×5,A＝6.143cm,i＝1.25cm,i＝1.94cm D.1L70×5,A＝6.87cm,i＝1.39cm,i＝2.16cm