The correct answer is (a). Ice cores provide a continuous record of the Earth’s climate over thousands of years. They can be used to study changes in temperature, precipitation, and atmospheric composition. Ice cores also contain information about past volcanic eruptions, solar activity, and changes in sea level.
Fossilized pollen can be used to study changes in vegetation over time. It can also be used to track the spread of diseases and the migration of animals. Tree ring growth can be used to study past climate conditions. Tree rings are wider in years with more rainfall and narrower in years with less rainfall. Evaporite deposits are formed when water evaporates from a lake or ocean. They can be used to study changes in sea level and climate.
In conclusion, ice cores are the best indicator of climate change because they provide a continuous record of the Earth’s climate over thousands of years.