Quicksand is a flow condition that occurs in cohesionless soils, which means that the correct answer is option 'C'.

Quicksand is a fascinating natural phenomenon that has been portrayed in movies and literature as a dangerous trap from which escape seems impossible. However, it is important to understand the science behind quicksand to dispel any misconceptions and understand how to react if one ever encounters it.

Flow Condition in Cohesionless Soils:
Quicksand is a type of flow condition that occurs in cohesionless soils. Cohesionless soils are composed of loose particles, such as sand or silt, that do not stick together. These particles have little to no cohesion and rely mainly on frictional forces to maintain their stability.

Key Characteristics of Quicksand:
1. Suspension of Soil Particles: Quicksand is characterized by the suspension of soil particles in water. When water saturates the loose soil, it reduces the friction between the particles, causing them to lose their ability to support weight effectively.

2. Decreased Soil Strength: As the water content increases, the soil loses its strength and behaves more like a liquid than a solid. This decrease in soil strength is what causes individuals or objects to sink when they come into contact with quicksand.

3. Density and Viscosity: Quicksand has a higher density and viscosity compared to normal water-saturated soil. This increased density and viscosity contribute to the sinking effect experienced in quicksand.

4. Buoyancy Effect: The buoyancy effect in quicksand is also noteworthy. When a person or object is submerged in quicksand, the upward buoyant force reduces the effective weight, making it more difficult to escape.

Precautions and Escape Techniques:
1. Avoid Panicking: Panicking can lead to further sinking in quicksand. It is crucial to stay calm and avoid sudden movements that can increase the suction effect.

2. Spread Weight: Instead of trying to forcefully lift a leg or body part out of quicksand, spreading weight by lying on your back or slowly floating on your back can help distribute the pressure and increase the chances of staying afloat.

3. Slowly Extracting Body Parts: If sinking has occurred, it is recommended to slowly extract body parts in a horizontal or diagonal direction to minimize the suction effect and prevent further sinking.

In conclusion, quicksand is indeed a flow condition that occurs in cohesionless soils. Understanding its characteristics and knowing the appropriate precautions and escape techniques can help individuals stay safe if they ever encounter quicksand.