Concept:Block mountains are landforms created by faulting, where large crustal blocks are displaced vertically.
Explanation:Block mountains, also known as horsts, form when powerful internal forces fracture the Earth's crust along parallel fault lines.
These faults divide the crust into blocks. When the central block is pushed or uplifted higher than the blocks on either side, a block mountain is created.
The adjacent lowered blocks become rift valleys or grabens. This process is driven by tensional forces in the lithosphere.
It is not caused by volcanic accumulation, magma solidification, or sediment movement in geosynclines.
Therefore, the key condition is the uplifting of a crustal block between two parallel faults.
Answer:C. uplifting of crustal block within two parallel faults