In order of increasing percentage of silica, the correct sequence is A. Sandy clay, calcareous clay, pure clay B. Calcareous clay, pure clay, sandy clay C. Pure clay, sandy clay, calcareous clay D. None of these

The correct answer is: C. Pure clay, sandy clay, calcareous clay

Silica is the main component of clay, and its percentage in clay can vary depending on the type of clay. Pure clay contains the highest percentage of silica, followed by sandy clay and calcareous clay.

Sandy clay contains a significant amount of sand, which is made up of quartz particles. Quartz is a mineral that is composed of silicon dioxide, which is also the main component of silica. Therefore, sandy clay contains less silica than pure clay.

Calcareous clay contains calcium carbonate, which is a mineral that is composed of calcium and carbon dioxide. Calcium carbonate is not a component of silica, so calcareous clay contains the least amount of silica.

In conclusion, the correct sequence of increasing percentage of silica is:

1. Pure clay
2. Sandy clay
3. Calcareous clay