Which of the Following Accurately Describes ¹³C/¹²C Ratios of Plant

Which of the following accurately describes ¹³C/¹²C ratios of plant materials and their use in climate reconstructions?

A) ¹³C is an unstable isotope,which decays at a constant rate.This is used to date plant material,which can then be used as a proxy for temperature and climate conditions at that time.
B) By analyzing the ratio of¹³C/¹²C in marine phytoplankton,the source of the water in which the organisms resided can be determined.
C) ¹²C is very rare in nature.When it does appear in plant material,it is indicative of climate anomalies.By measuring the ¹³C/¹²C ratios,scientists can determine whether the plants were alive during normal or anomalous conditions.
D) Different plants use different types of photosynthesis,each producing a different carbon isotope ratio in plant materials,which scientists use to determine past temperature and rainfall conditions.