D.yes its because all of them have a knowledge to make valuable soil and not valuable they learn to a high level so i agree all of them

Classification of Soil Based on Particle Size

The classification of soil based on particle size is an essential aspect of soil engineering and geotechnical engineering. It helps in understanding and characterizing the soil's behavior, its suitability for various engineering applications, and its potential for erosion and drainage.

There are several systems used for the classification of soil based on particle size. The correct answer to the given question is option 'D' - All of the mentioned. Let's discuss each system in detail:

a) PRA System of the United States
- The PRA (Particle-Size Range Analysis) system is a classification system used in the United States.
- It categorizes soil based on particle size into groups such as gravel, sand, silt, and clay.
- Each group is further divided into subgroups based on the percentage of particles falling within specific size ranges.
- This system provides a standardized way to describe and classify soil based on its particle size distribution.

b) Indian Standard Classification System
- The Indian Standard Classification System is a widely used system in India for the classification of soil based on particle size.
- It classifies soil into four main groups: gravel, sand, silt, and clay.
- Each group is further divided into subgroups based on the percentage of particles falling within specific size ranges.
- This system is based on the percentage of particles retained on specific sieves during particle size analysis.

c) International Soil Classification
- The International Soil Classification system is a globally recognized system for classifying soil based on particle size.
- It is commonly referred to as the Unified Soil Classification System (USCS) and is widely used in geotechnical engineering.
- The USCS classifies soil into two main categories: coarse-grained soils and fine-grained soils.
- Coarse-grained soils are further classified based on the percentage of gravel, sand, and fines (silt and clay).
- Fine-grained soils are classified based on their plasticity and liquid limit.
- This system provides a comprehensive classification scheme that considers both the particle size distribution and the engineering behavior of the soil.

Conclusion
In conclusion, the classification of soil based on particle size is essential for understanding its engineering properties and behavior. Various systems are used for this purpose, including the PRA system of the United States, the Indian Standard Classification System, and the International Soil Classification system. Each system categorizes soil into different groups based on the percentage of particles falling within specific size ranges.