The correct answer is: A. Modular ratio method.
The modular ratio method is a method of calculating the equivalent concrete area of reinforced concrete (RCC) members. It is based on the assumption that the steel reinforcement in an RCC member carries all of the tensile stresses, while the concrete carries all of the compressive stresses. The equivalent concrete area is then calculated as the area of the steel reinforcement divided by the modular ratio, which is a dimensionless number that is equal to the modulus of elasticity of steel divided by the modulus of elasticity of concrete.
The load factor method is a method of calculating the strength of an RCC member. It is based on the assumption that the member will be subjected to a series of loads, each of which has a certain probability of occurring. The strength of the member is then calculated as the sum of the strengths of the member under each load, multiplied by the probability of that load occurring.
The ultimate load method is a method of calculating the ultimate load of an RCC member. It is based on the assumption that the member will fail when the maximum tensile stress in the concrete reaches the tensile strength of the concrete, or when the maximum compressive stress in the concrete reaches the compressive strength of the concrete.
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