某厂房的纵向天窗宽8m，高4m，采用彩色压型钢板屋面，冷弯型钢檩条。天窗架、檩条、拉条、撑杆和天窗上弦水平支撑局部布置简图如图1-4-11（α）所示；天窗两侧的垂直支撑如图1-4-11（6）所示；工程中通常采用的三种形式天窗架的结构简图分别如图1-4-11（c）、（d）、（e）所示。所有构件均采用Q235钢，手工焊接时使用E43型焊条，要求焊缝质量等级为二级。
在图1-4-11（d中，杆件CD的轴心压力很小（远小于其承载能力的50％），可按长细比选择截面，试问，下列何项截面较为经济合理？（）
A.A
B.B
C.C
D.D
参考答案：B
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"What a boring Christmas!" Tina thought to herself． At that moment，she 小题1: music in the street． She ran to the window and saw a little boy 小题2:．He was singing and beating a drum．Tina saw that he wore no 小题3: ． "Are you cold?" asked Tina． The little boy smiled，but she couldn't hear 小题4: he said．So she told him to come in． He was a little nervous，but the carpet (地毯) felt warm to 小题5: poor feet．He told Tina that his name was Guido．And he was very poor， 小题6: poor that he had to go singing from house to house for some money to buy his dinner．  "My mama is away，and I am 小题7: a sad Christmas．But I'll try to make it nice 小题8: you，" said Tina．They played games and Guido sang to her．Then they had a big dinner． Guido was very happy． That night，Tina told her mother， " Now I know something．Whenever you 小题9: sad and lonely，find somebody 小题10: and lonelier than yourself and cheer them up．It will make you feel all right． " |