Which of the following statements is/are not true?
1. Chemical weathering is most common in limestone rocks
2. Chemical weathering is most active in wet regions with higher temperature
3. Rain action is a form of chemical weathering
4. Exfoliation is a process of chemical weathering

Exfoliation is not a process of chemical weathering. Exfoliation can occur due to several processes. During a combination of physical and chemical weathering, exfoliation may occur parallel to a rock's outer surface due to a combination of chemical breakdown of minerals , especially in the presence of water.