Scientists have identified the past changes in the climatic conditions that occurred because of the following reasons. These includes:
Milankovitch cycles: These cycles are related with the orbit motion and tilt of the earth that occur in every 100,000 years, believed to be responsible for the past ice ages. The formation of the ice age is likely to affect the past climatic conditions.
Thermohaline circulation: It is the circulation of water which influences the temperature and salt content of the water body or a terrestrial land.
Plate tectonics and volcanic activity: The plate tectonics is related with the splitting apart or movement of the large continental and oceanic plates over the surface of the lithosphere. It is related with the intense seismic activity that is occurrence of earthquakes and eruption of volcanoes. The volcanoes could have influenced the climatic conditions in the past. The release of the dust particles and gases thrown into the atmosphere due to the eruption being added up with the atmosphere may either heat up the surrounding air or may cause cooling.
A niche refers to the way in which an organism fits into an ecological community or ecosystem. How an organism interacts with it's environment. So, I believe the answer to be C.
