What type of soil passes the No. 4 sieve and is retained on the No. 40 sieve?

The correct answer is coarse sand because this specific type of soil is characterized by its grain size, which allows it to pass through a No. 4 sieve. The No. 4 sieve has a mesh opening of 4.76 mm, which means that particles of coarse sand are small enough to pass through this sieve. However, these particles are larger than the mesh size of the No. 40 sieve, which has a mesh opening of 0.425 mm, meaning that coarse sand is too large to pass through it and is therefore retained.

To further clarify, other types of soils mentioned do not meet these criteria. For example, silt consists of finer particles that would pass through both sieves. Organic soil can contain varying particle sizes but often includes decomposed materials, which are also less likely to fit neatly within the size restrictions of the question. Gravel, on the other hand, typically consists of larger particles that would not pass through a No. 4 sieve at all. Understanding the specific sieve sizes helps in identifying the correct type of soil based on particle size retention and passage.