To determine the correct answer regarding the diameter of the soil particle that would be retained in the part labeled II of the diagram, we need to understand the classification of soil particles based on their size. Soil particles are typically categorized into three main groups: sand, silt, and clay. Each of these groups has a specific size range. Explanation of the Correct Answer Correct Option: B. 0.02 - 0.2 mm

1. Understanding Soil Particle Sizes:
2. Clay: Particles smaller than 0.002 mm (2 micrometers).
3. Silt: Particles ranging from 0.002 mm to 0.02 mm.
4. Sand: Particles ranging from 0.02 mm to 2.0 mm.
5. Gravel: Particles larger than 2.0 mm.

Based on this classification, the range of 0.02 - 0.2 mm falls within the sand category, which is the size of particles that would be retained in the section labeled II.

1. Why Option B is Correct:
2. The range of 0.02 - 0.2 mm corresponds to the lower end of the sand particle size. This means that any soil particle within this size range will be retained in the section labeled II, which is designed to filter out smaller particles (like silt and clay) and allow larger particles (like sand) to pass through.

Explanation of Incorrect Options

• Option A: 0.002 - 0.02 mm:
• This range corresponds to silt and clay particles. Since the question specifies the size of particles retained in section II, which is meant for sand, this option is incorrect. Particles in this range would not be retained in section II.
• Option C: 0.2 - 2.0 mm:
• This range includes larger sand particles and even gravel. While particles in this range may be retained in a different section, they exceed the upper limit of the size range specified for section II. Therefore, this option is also incorrect.
• Option D: 2.0 mm:
• This option refers to particles that are classified as gravel. Since section II is not designed to retain such large particles, this option is incorrect as well.

Summary of Key Points

• Soil particles are classified into categories based on size: clay (<0.002 mm), silt (0.002 - 0.02 mm), sand (0.02 - 2.0 mm), and gravel (>2.0 mm).
• The correct answer for the diameter of soil particles retained in section II is 0.02 - 0.2 mm, which corresponds to sand.
• Options A, C, and D are incorrect because they either refer to smaller particles (A), larger particles (C), or gravel (D), which do not fit the criteria for section II.

Revision Summary

• Soil particle sizes: Clay (<0.002 mm), Silt (0.002 - 0.02 mm), Sand (0.02 - 2.0 mm), Gravel (>2.0 mm).
• Correct answer for section II: B. 0.02 - 0.2 mm (sand).
• Incorrect options: A (silt/clay), C (larger sand/gravel), D (gravel).
• Understanding soil particle classification is crucial for analyzing soil samples effectively.