A low Si-sesquioxide ratio in soil typically indicates:

• The Si-sesquioxide ratio refers to the ratio of silicon (Si) to sesquioxides (Fe₂O₃, Al₂O₃, and other oxides of iron and aluminum) in soil. A low Si-sesquioxide ratio typically indicates that the soil has undergone significant weathering. This is because:
-High weathering leads to the depletion of silica (Si) while the concentration of sesquioxides (iron and aluminum oxides) increases. This is typical of highly weathered soils, such as Oxisols and Ultisols, which are often found in tropical regions.
-Conversely, less weathering would retain a higher amount of silicon relative to sesquioxides, as in soils found in less weathered regions or regions with less intense weathering processes.

📌Other Options Explanations:
(b) Least weathering: A low Si-sesquioxide ratio is associated with high weathering.

🛑 Additional Information:: Weathering:
-Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms.
-Weathering occurs in situ (on-site), that is, in the same place.
-Weathering is a result of exogenetic forces.
-It can be physical and chemical weathering.
-Physical or mechanical weathering happens when a rock is broken through the force of another substance on the rock such as ice, running water, wind, rapid heating/cooling, or plant growth.
-Chemical weathering occurs when reactions between a rock and another substance dissolve the rock, causing parts of it to fall away.