The correct answer is A. 2800/C.
The modular ratio is a dimensionless number that is used to compare the stiffness of concrete and steel. It is defined as the ratio of the modulus of elasticity of concrete to the modulus of elasticity of steel. The modulus of elasticity of concrete is typically about 28,000 MPa, while the modulus of elasticity of steel is typically about 200,000 MPa. Therefore, the modular ratio is typically about 0.14.
The modular ratio is used in the design of reinforced concrete beams to determine the effective depth of the beam. The effective depth is the depth of the beam that is effectively resisting bending. The effective depth is determined by dividing the moment of resistance of the beam by the axial load on the beam. The moment of resistance of the beam is determined by multiplying the modular ratio by the area of steel in the beam.
The modular ratio is also used in the design of concrete slabs to determine the thickness of the slab. The thickness of the slab is determined by dividing the live load on the slab by the bending stress in the slab. The bending stress in the slab is determined by multiplying the modular ratio by the effective depth of the slab.
The modular ratio is an important factor in the design of reinforced concrete structures. It is used to determine the effective depth of beams and slabs, and it is also used to determine the amount of steel reinforcement that is required.
The other options are incorrect because they do not represent the correct relationship between the modulus of elasticity of concrete and the modulus of elasticity of steel.