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
(d) Neither Statement II nor StatementIII is correct

The correct answer is (c) Only one of the Statements II and III is correct and that explains Statement I.

Explanation

Analyze 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.”
- This statement is Correct.
- Chalk is a type of limestone that is highly fractured, which allows water to pass through it easily, making it permeable (it’s a good aquifer).
- Clay is made of microscopic, flat particles. Water gets trapped in the tiny spaces (it’s porous), but these spaces are not well-connected, making it very difficult for water to flow. Thus, it is impermeable (it’s an aquiclude).
Analyze Statement II: “Chalk is porous and hence can absorb water.”
- This statement is Correct. Chalk, being a sedimentary rock, has small spaces (pores) within its structure that allow it to hold water. This property is porosity.
Analyze Statement III: “Clay is not at all porous.”
- This statement is Incorrect. This is a common misconception. Clay actually has very high porosity (a large volume of pore space) and can hold a lot of water. Its key feature is its low permeability (the pores aren’t connected, so water can’t flow through).

Evaluating the Options

Since only Statement II is correct and Statement III is incorrect, the assertion “Only one of the Statements II and III is correct” is true.
This immediately eliminates options (a), (b), and (d), which are all based on false premises.
Therefore, (c) is the only logically possible answer. The reasoning is that Statement II (chalk being porous) is the correct explanation for its properties in Statement I, whereas Statement III (clay not being porous) is an incorrect explanation for its properties.