**Liquid Limit of Soils**

The liquid limit is a property of soils that represents the moisture content at which the soil transitions from a plastic state to a liquid state. It is an important parameter in geotechnical engineering as it helps determine the soil's behavior and shear strength.

**Shear Strength of Soils**

Shear strength is the resistance of a soil to shearing forces. It is a crucial factor in determining the stability of slopes, retaining walls, and foundations. Shear strength of soils is influenced by various factors including the soil type, density, moisture content, and stress conditions.

**Explanation of Answer**

The correct answer to the given question is option 'A': Same shear strength of small magnitude. This means that at the liquid limit, all soils possess the same shear strength, but it is of relatively small magnitude.

This answer is based on the behavior of soils at the liquid limit. When a soil reaches its liquid limit, it becomes highly saturated with water and loses its ability to resist shear stresses effectively. At this moisture content, the soil particles are suspended in water, causing a decrease in the soil's cohesion and shear strength.

**Reasoning behind Option A**

The reason why all soils possess the same shear strength at the liquid limit is primarily due to the loss of cohesion. Cohesion is the component of shear strength that arises from interparticle attractive forces in cohesive soils. These attractive forces are mainly due to the bonds between particles, such as clay minerals.

When a soil is in a plastic state, it can resist shearing forces to some extent due to cohesion. However, as the moisture content increases and the soil transitions to the liquid state at the liquid limit, the cohesive forces between particles are greatly reduced. This reduction in cohesion results in a decrease in shear strength.

**Magnitude of Shear Strength**

The shear strength at the liquid limit is of relatively small magnitude compared to the shear strength of soils in a consolidated or semi-solid state. This is because the soil is in a highly saturated and loose state at the liquid limit, which leads to a lower resistance to shearing forces.

In contrast, soils in a consolidated or semi-solid state, such as those with lower moisture contents, have higher shear strengths. The particles in these soils are more closely packed, leading to increased frictional forces and interparticle bonding, which contribute to higher shear strength.

**Conclusion**

In summary, at the liquid limit, all soils possess the same shear strength of small magnitude due to the loss of cohesion. This is because the soil is in a highly saturated and loose state, leading to a decrease in shear strength compared to soils in a more consolidated or semi-solid state. Understanding the behavior of soils at different moisture contents is essential for geotechnical engineers to design safe and stable structures.

Liquid limit is the maximum water content at which soil still exists as a solid. Beyond which the soil is technically a liquid. Shear force doesn't exist in liquids.