Final answer:
An inselberg is an island mountain made of hard rocks such as granite or gneiss, rising from softer rocks of the plain. The correct option for the geographical feature described is 'a. inselberg'.
Step-by-step explanation:
The mountain formation described in the question is known as an inselberg, which is typically an isolated hill or a lone mountain that rises abruptly from a gently sloping or virtually level surrounding plain. Inselbergs are usually composed of hard rocks like granite or gneiss, which are more resistant to erosion compared to the rocks of the surrounding plains.
As a result, they withstand the forces of weathering better than their surroundings, which are more easily worn away over time. The processes of erosion, particularly by water and ice, carve and shape the landscapes, creating the distinctive inselbergs that stand prominently above the surrounding terrain. For example, in a place like Borneo where tectonic plate activity has shaped the landscape, the ancient rocks have been worn down by erosion to create mountainous regions.
The terms mesa, glacier, and burger do not represent the geographical feature described. A mesa is a flat-topped hill with steep sides, typically found in arid landscapes, while a glacier is a massive body of ice moving slowly over land. Burger does not correspond to any geographical term related to mountain formation.
Therefore, the correct option for the question is: a. inselberg.