Answer:
Sediments are used to provide the proxies to understand the environmental changes as, the sediments are formed by the activity of the weathering from the wind, glacier and the water. The different weathering agent and other transportation agent are different types of the mark over the sediments that help in the study of the past environment.
After reviewing the graph you have given with the question, there are several reasons why carbon 14 can't be used to accurately determine the age of organic remains that are 1 million years old.
A few of the reasons are; Carbon-14 has a short half life, after 1,000,000 years there wouldn't be enough carbon 14, and too little of the original radioactive sample would remain. Any of these choices are correct for the answer to the question you asked.
The Ming emperors made it their capital in 1421 and it remained China's capital till 1912 when the Manchu Empire fell and SunYat Sen turned China into a republic.
