Cohesionless soil, also known as granular soil, refers to soil that does not have any cohesive properties and is composed of individual particles. It is characterized by the absence of stickiness or plasticity when wet, and it cannot be molded or shaped. Cohesionless soil is commonly found in riverbeds, beaches, and deserts.

The correct answer to this question is option 'B', which is sand. Sand is a type of cohesionless soil that consists of loose, granular particles. It is formed by the erosion and weathering of rocks, and its particle size ranges from 0.0625 mm to 2 mm.

Here is a detailed explanation of why sand is considered a cohesionless soil:

1. Definition of Cohesionless Soil:
- Cohesionless soil refers to soil that lacks cohesive properties, which means the particles do not stick together or have any interparticle bonding.
- It is composed of individual particles that are not strongly held together.

2. Characteristics of Cohesionless Soil:
- Granular particles: Cohesionless soil is made up of loose, granular particles with little or no cohesion between them.
- Non-plastic: It cannot be molded or shaped when wet.
- Drains water easily: Cohesionless soil has high permeability, allowing water to flow through it easily.
- High porosity: It has a high percentage of void spaces between particles, which allows for good drainage.

3. Sand as Cohesionless Soil:
- Sand is a common example of cohesionless soil.
- It is composed of individual sand grains, which are typically larger than the particles found in other types of soil.
- Sand particles are coarse and have a low surface area, resulting in low adhesion and cohesion forces between them.
- Due to its granular nature, sand does not exhibit plasticity or stickiness when wet.

In conclusion, cohesionless soil refers to soil that lacks cohesive properties and is composed of loose, granular particles. Sand is a type of cohesionless soil that exemplifies these characteristics, making it the correct answer in this context.