The correct answer is option 4: Exfoliation. Exfoliation is not a process of chemical weathering, but rather a physical weathering process.

Chemical weathering refers to the breakdown of rocks and minerals through chemical reactions. It occurs when minerals within the rocks react with water, air, or other chemicals in the environment. This can cause changes in the composition and structure of the rocks. Two of the options, namely options 2 and 3, are examples of chemical weathering processes.

Option 2: Carbonation, refers to the reaction between carbon dioxide (CO2) in the air and water to form carbonic acid. This acid can dissolve minerals in rocks, particularly limestone and other carbonate rocks, leading to their weathering.

Option 3: Oxidation, involves the reaction of minerals with oxygen. This can cause the minerals to change chemically and weaken the structure of the rocks. An example of oxidation is the rusting of iron.

Option 4: Exfoliation, on the other hand, is a physical weathering process. It refers to the peeling or flaking of layers of rock from the surface of a larger rock mass. Exfoliation is typically caused by the expansion and contraction of rock due to heating and