If the modular ratio is m, steel ratio is r and overall depth of a beam is d, the depth of the critical neutral axis of the beam, is

• A. <img src="/_files/images/civil-engineering/rcc-structures-design/69-13-4-1.png">
• B. <img src="/_files/images/civil-engineering/rcc-structures-design/69-13-4-2.png">
• C. <img src="/_files/images/civil-engineering/rcc-structures-design/69-13-4-3.png">
• D. <img src="/_files/images/civil-engineering/rcc-structures-design/69-13-4-4.png">
• E. <img src="/_files/images/civil-engineering/rcc-structures-design/69-13-4-5.png">