(i) The centre of the Earth, lying about 6000 km from the ocean floor, is characterised by extremely high temperature and pressure. There is only molten magma at Earth’s centre. Oxygen is absent from this region. Such conditions do not permit the survival of any living organism. Thus, we cannot go to the centre of the Earth.
(ii) When big rocks break down into small fragments (or sediments), the fragments are transported and deposited by factors like water and wind. The loose sediments compress and harden over the years to form layers and layers of rocks. These rocks are known as sedimentary rocks.
(iii) Limestone is an example of a sedimentary rock. When it is subjected to conditions of extreme heat and pressure, it gets converted into marble, which is a metamorphic rock.