In beams, the maximum area of the reinforcement in tension reinforcement should not exceed 0.04 bD. Let's break down the answer and understand it in detail.

- Definition and Importance of Tension Reinforcement in Beams:
Tension reinforcement is the reinforcement provided in the bottom part of a beam to resist the tensile forces that develop due to bending. It is essential to prevent the formation of cracks and ensure the stability and strength of the beam.

- Maximum Area of Tension Reinforcement:
The maximum area of the reinforcement in tension reinforcement is specified to prevent excessive reinforcement, which can lead to issues such as congestion, difficulty in construction, and reduced bond strength between the reinforcement and concrete.

- Calculation of Maximum Area:
The maximum area of tension reinforcement is given by the formula: Ast(max) = 0.04 bD, where Ast(max) represents the maximum area of tension reinforcement, b is the width of the beam, and D is the effective depth of the beam.

- Explanation of the Formula:
The formula indicates that the maximum area of tension reinforcement is directly proportional to the product of the beam's width and effective depth. The value 0.04 is a coefficient that ensures a balanced design and considers various factors such as crack control, constructability, and bond strength.

- Significance of the Coefficient:
The coefficient 0.04 is derived from extensive research and practical experience to provide a suitable limit for the maximum area of tension reinforcement. It ensures that the reinforcement is adequately distributed and avoids excessive reinforcement, which can lead to problems during construction and compromise the performance of the beam.

- Other Options:
Options B, C, and D are incorrect because they provide lower values for the maximum area of tension reinforcement. If these options were chosen, it would result in inadequate reinforcement, potentially leading to cracking, reduced strength, and structural failure.

- Conclusion:
In conclusion, the correct answer is option A, which states that the maximum area of reinforcement in tension reinforcement should not exceed 0.04 bD. This limit ensures a proper balance between reinforcement requirements and constructability, ultimately leading to a safe and efficient beam design.