The limit state method and working stress method are two different approaches used in the design of reinforced concrete structures. The main difference between these two methods lies in how they consider the behavior and strength of the materials used.

1. Working Stress Method:
- The working stress method, also known as the allowable stress design method, is an older approach that was widely used in the past.
- In this method, the design is based on the allowable stresses that the materials can safely withstand.
- The stresses are determined based on the elastic properties of the materials, and a factor of safety is applied to ensure structural integrity.
- The design is conservative, with a focus on preventing the materials from reaching their ultimate limit states.
- The main idea behind this method is to ensure that the structure can safely support the applied loads without excessive deformation or failure.

2. Limit State Method:
- The limit state method is a more modern and rational approach to design.
- It takes into account both the strength and serviceability requirements of the structure.
- The design is based on the concept of limit states, which are conditions beyond which the structure is deemed to have failed.
- The limit states include the ultimate limit state (ULS) and the serviceability limit state (SLS).
- In the ULS, the structure is evaluated for strength and stability under the most severe loads.
- In the SLS, the structure is evaluated for deflection, cracking, and other deformations that may affect its serviceability.
- The design is carried out by ensuring that the probability of reaching a limit state is sufficiently low.

Explanation of the correct answer:
- In the limit state method, the design takes concrete to a higher stress level compared to the working stress method.
- This is because the limit state method considers the full strength of the concrete and allows it to be stressed up to its ultimate capacity.
- The design is based on the ultimate limit state, where the structure is evaluated for its strength and stability under the most severe loads.
- By allowing the concrete to be stressed up to its ultimate capacity, the limit state method optimizes the design, resulting in more efficient and economical structures.
- In contrast, the working stress method limits the stress in the concrete to a lower level based on the allowable stresses.
- This conservative approach ensures a higher factor of safety but may result in overdesign and unnecessary use of materials.

In conclusion, the limit state method takes concrete to a higher stress level compared to the working stress method. This allows for a more efficient and economical design while still ensuring the structural integrity and safety of the reinforced concrete structure.

Because in working stress method the stress is lower while in lsm we use the max value of stress so we can use maximum strength of the materia as compared to working Stress method