Which of the following statements is true about particle sizes in soils?

• A. Clay is the smallest particle, followed by silt and sand
• B. Sand is the smallest particle, followed by silt and clay
• C. Silt is the smallest particle, followed by clay and sand
• D. Clay and sand are smaller than silt

Answer: (A)

In soils, particle size from smallest to largest is clay, then silt, then sand. Clay particles are extremely tiny—less than about 0.002 mm in diameter. Silt is larger, roughly 0.002 to 0.05 mm, and sand is even larger, about 0.05 to 2 mm. So saying that clay is the smallest particle, followed by silt and then sand is correct.

This order helps explain soil behavior: the tiny clay particles create high surface area and strong cohesion when wet, influencing water retention and plasticity; sand drains quickly and has low surface area; silt falls in between. The other statements conflict with these size ranges.