The correct order of grain size in decreasing size is:
c) Sand-Pebble-Clay-Silt
In this order, sand grains are larger than pebble grains, pebble grains are larger than clay grains, and clay grains are larger than silt grains.
To understand this concept better, let's look at each term in the list:
- Sand: Sand grains are larger than pebble, clay, and silt grains. They are typically between 0.05 mm and 2 mm in size. Think of the sand you find on beaches or in sandboxes.
- Pebble: Pebble grains are larger than clay and silt grains. They are generally between 4 mm and 64 mm in size. Pebbles are larger than sand grains and are often found in riverbeds or on rocky shores.
- Clay: Clay grains are smaller than pebble and sand grains. They are typically less than 0.002 mm in size. Clay feels smooth and sticky when wet, and it is often used in pottery.
- Silt: Silt grains are smaller than clay grains but larger than clay particles. They are between 0.002 mm and 0.05 mm in size. Silt feels smooth and powdery. It can be found in river sediments and on the banks of lakes.
So, in summary, the correct order of grain size in decreasing size is sand, pebble, clay, and silt, which corresponds to option c) Sand-Pebble-Clay-Silt.