如图5-7-5所示，矩形截面杆AB，A端固定，B端自由，B端右下角处承受与轴线平行的集中F，杆的最大正应力是（　　）。[2010年真题]图5-7-5

A、<img width="49" height="31" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/40114811-19d2-483c-a7a6-dccb5e732420.png" />

B、<img width="44" height="32" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/ca99476f-9693-475d-9b20-c46827e9790b.png" />

C、<img width="45" height="31" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/5486cf21-d9ee-4f05-ab27-33057a406257.png" />

D、<img width="53" height="31" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/8fd2e0d2-105c-4593-8cc9-8321a7ba31fa.png" />