图示刚架，EI=常数，B点的竖向位移（↓）为：（）<img src="/Image1/ca/ca86cddd56dcd48c41e05fb61b822f00.jpg" /><br>A:Pl<sup>3</sup>／6EI<br>B:<img src="/Image1/6a/6a946cc9da991b8deb04cde5360cc170.jpg" />Pl<sup>3</sup>／3EI<br>C:<img src="/Image1/6a/6a946cc9da991b8deb04cde5360cc170.jpg" />Pl<sup>3</sup>／6EI<br>D:Pl<sup>3</sup>／3EI