Consider the following statements : Statement I : In the context of effect of water on rocks, chalk is known as a very permeable rock whereas clay is known as quite an impermeable or least permeable rock. Statement II : Chalk is porous and hence can absorb water. Statement III : Clay is not at all porous. Which one of the following is correct in respect of the above statements?
A
Both Statement II and Statement III are correct and both of them explain Statement I
B
Both Statement II and Statement III are correct but only one of them explains Statement I
C
Only one of the Statements II and III is correct and that explains Statement I
Correct Answer
D
Neither Statement II nor Statement III is correct
Explanation
Option (C) is correct because Statement II is factually true—chalk is porous and permeable—while Statement III is false because clay is actually highly porous, despite being impermeable. Option (A) is the most tempting wrong choice because it relies on the common misconception that impermeability implies a lack of porosity; in reality, clay has high porosity but low permeability because its pores are too small and disconnected to allow water flow. The core concept being tested is the distinction between porosity (the capacity to hold water) and permeability (the ability to transmit water) in sedimentary rocks.
Physical GeographyRocks and MineralsPermeabilityPorosityChalkClayHydrology