Statement I : By far the most common topographic form in a Karst terrain is the sinkhole. Statement I : Topographically, a sinkhole is a depression that varies in depth from less than a meter to few hundred meters.

Statement I is true as sinkholes (or dolines) are recognized as the most common and characteristic topographic form in karst terrain. They are fundamental features created by the dissolution of soluble bedrock like limestone [2]. Statement II is also true; topographically, a sinkhole is an enclosed depression that exhibits significant variation in scale, ranging from less than a meter to several hundred meters in depth and diameter [3]. While Statement II accurately describes the physical dimensions and nature of a sinkhole, it does not explain why it is the 'most common' form. The prevalence of sinkholes (Statement I) is due to the widespread chemical weathering and dissolution processes inherent in karst landscapes, rather than their specific depth range. Therefore, both statements are individually true, but Statement II is not the correct explanation of Statement I.

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 17: Major Landforms and Cycle of Erosion > 17.2. Karst Landforms and Cycle of Erosion > p. 226
2. [3] https://www.nps.gov/subjects/caves/karst-landscapes.htm