The correct answer is option 'A' - Mid span.

Flexural cracks in reinforced concrete (RCC) members, such as beams, are primarily formed at the mid span. This is due to the distribution of bending moments in a simply supported beam.

Here's an explanation of why flexural cracks form at the mid span:

1. Bending Moment Distribution: In a simply supported beam, the bending moment is maximum at the mid span and decreases towards the supports. This is because the load is applied at the mid span and is distributed towards the supports. As a result, the beam experiences maximum bending stress at the mid span.

2. Maximum Tensile Stress: The bottom fibers of the beam experience tensile stress due to the bending moment. The maximum tensile stress occurs at the bottom fiber of the beam at the mid span. This is where the flexural crack initiates.

3. Neutral Axis: The neutral axis is the line along the depth of the beam that experiences no stress. In a simply supported beam, the neutral axis is located at the mid depth of the beam. The flexural crack forms on the bottom fiber, which is further away from the neutral axis, as this is where the tensile stress is maximum.

4. Cracking due to Tensile Stress: Concrete is strong in compression but weak in tension. When the tensile stress exceeds the tensile strength of concrete, cracking occurs. At the mid span of a beam, the tensile stress is higher compared to the other regions, leading to the formation of flexural cracks.

5. Shear Cracks: It is important to note that in addition to flexural cracks, beams can also develop shear cracks near the supports. Shear cracks occur due to the shear forces acting on the beam. However, the question specifically asks about flexural cracks, which are formed at the mid span.

In summary, flexural cracks in RCC members, such as beams, are formed at the mid span due to the maximum bending moment and tensile stress at that location. These cracks occur when the tensile stress exceeds the tensile strength of concrete.