The critical load for a column of length I hinged at both ends and having flexural rigidity El, is given by

• A. <img src="/_files/images/civil-engineering/steel-structure-design/95-14-49-1.png">
• B. <img src="/_files/images/civil-engineering/steel-structure-design/95-14-49-2.png">
• C. <img src="/_files/images/civil-engineering/steel-structure-design/95-14-49-3.png">
• D. none of these