Consider the following statements: Which one of the following is correct in respect of the above statements?

Answer: (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I

Carbonation (CO₂) and oxidation (O₂) both cause weathering.

Statement by statement

1. ✓ CORRECT Rain weathers rock physically and chemically.

2. ✓ CORRECT Dissolved CO₂ makes rain a weak carbonic acid that dissolves limestone (carbonation).

3. ✓ CORRECT Dissolved oxygen oxidises iron minerals — rusting of rock (oxidation).

The idea

Chemical weathering changes the minerals in rock without requiring the rock to be carried away. Water provides a medium in which dissolved gases react with minerals. Different reactions can act on the same exposed surface at the same time.

Rain takes up gases from air → Water reaches exposed rock and cracks → Dissolved gases react with suitable minerals → Some minerals dissolve or form new compounds → Rock weakens → Loose material becomes available for erosion

Why the others are wrong

(b) Both II and III explain I — not only one.

(c) Both are correct.

(d) Both are correct.

The trap

“Only one explains” is the careful-sounding trap. Both gases do chemical work.

Also know

Mechanical weathering breaks rock without changing its mineral composition; freeze-thaw is one example. Hydrolysis changes minerals such as feldspar into clay minerals. Limestone dissolution creates karst features such as sinkholes and caves. Weathering occurs in place, while erosion includes removal and transport.