The moisture content between which two states defines the plastic limit?

The correct choice defines the plastic limit as the moisture content between the plastic state and the semisolid state of soil. At the plastic limit, the soil begins to transition from a plastic behavior—where it can be molded and retains shape when stressed—to a semisolid state, which indicates it is less workable and may crumble or crack under pressure.

Understanding this transition is crucial in soil mechanics because it helps determine the soil's workability and its behavior in various engineering applications. The plastic limit indicates the upper moisture content at which the soil still exhibits plasticity before becoming too dry and losing its ability to deform without cracking.

Other options do not accurately describe the boundaries that define the plastic limit. They either overlap with other states, such as the liquid limit or do not accurately represent the specific transition between states relevant to the plasticity of soil.