Explanation

The plastic limit is the moisture content below which a cohesive soil ceases to be plastic and begins to crumble. While 'sticky limit' is sometimes used in older texts to describe the point where soil stops sticking to metal, the standard geotechnical term for the boundary between semi-solid and solid states (where stickiness disappears) is often associated with the shrinkage limit or plastic limit depending on context. However, strictly speaking, the moisture content below which soil does not stick to metal tools is technically defined as the 'Sticky Limit' in some specific contexts, but standard Atterberg limits are Liquid, Plastic, and Shrinkage. Let's re-evaluate. The sticky limit is the water content at which the soil ceases to be sticky. It is generally higher than the plastic limit. The question asks for the moisture content below which it does NOT stick. This matches the definition of the Sticky Limit. Wait, standard Atterberg limits are Liquid Limit (LL), Plastic Limit (PL), and Shrinkage Limit (SL). 'Sticky Limit' is a recognized term in some literature (e.g., Casagrande) defined as the water content below which soil loses its stickiness. It is usually between LL and PL. If the question specifically asks for the limit where it stops sticking to metal, 'Sticky Limit' is the precise definition. However, many modern exams might consider 'Plastic Limit' or 'Shrinkage Limit' depending on the specific curriculum. But 'Sticky Limit' is the exact term for loss of stickiness. Let's check standard definitions. Sticky limit: The moisture content below which soil ceases to be sticky. This matches option C exactly. Therefore, C is likely correct. I will verify if 'Sticky Limit' is a standard accepted answer in Pakistani MCQs. Yes, it appears in civil engineering MCQs. So C is correct.