The correct option is (b).
Explanation
The Earth's crust is the outermost solid shell of the planet. It is brittle in nature and varies significantly in thickness and composition between continental and oceanic areas.Statement 1 is Incorrect: The Earth's crust is not a single continuous solid block. The lithosphere, which includes the crust and the uppermost solid mantle, is broken into numerous large and small fragments known as lithospheric or tectonic plates. These plates move relative to one another.
Statement 2 is Correct: The continental crust is thicker and less dense than the oceanic crust. It is primarily composed of granitic rocks, which are rich in Silica and Alumina. Consequently, it is often referred to as SIAL.
Statement 3 is Incorrect: The oceanic crust is significantly thinner than the continental crust. The average thickness of the oceanic crust is approximately 5 km, whereas the continental crust averages around 30 km (and can exceed 70 km in major mountain systems). The oceanic crust is composed mainly of basaltic rocks rich in Silica and Magnesium (SIMA).
Key Takeaway: The continental crust (SIAL) is thicker and less dense, while the oceanic crust (SIMA) is thinner and denser. The Earth's outer shell is fragmented into tectonic plates rather than being a single solid block.