Statement I : The process of decay and disintegration of rocks in situ is called weathering. Statement I : Weathering takes place both mechanically and chemically.

Statement I is true as weathering is defined as the mechanical disintegration and chemical decomposition of rocks through the actions of weather and climate elements [3]. It is specifically an in-situ or on-site process because very little to no motion of materials occurs during the breakdown [3]. Statement II is also true, as weathering processes are categorized into three major groups: chemical, physical (mechanical), and biological [1]. While both statements are factually correct, Statement II is not the 'explanation' for Statement I. Statement II describes the modes or types of weathering, whereas Statement I provides the definition and spatial characteristic (in-situ) of the process. The fact that weathering occurs mechanically or chemically does not explain why it is an in-situ process; rather, the lack of transport agents during the breakdown defines its in-situ nature [3].

Sources

1. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Weathering > p. 82
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Weathering > p. 83