200
Which best describes how ice cores are important to the study of geologic history?
A They show unconformities, which signal changes in deposition.
B They hold index fossils, which are used to date the different ice cores.
C They contain evidence showing changes in the atmospheric composition over
time.
D They follow the Law of Superposition, which gives reasons for extinctions of
species.
C They contain evidence showing changes in the atmospheric composition over
time.