Which of these explain how ice cores can be used to correlate atmospheric makeup and climate changes over time?

A) As ice melts into water, the thermal expansion traps gases from the atmosphere that can later be analyzed

B)As ice forms, a latent heat is released from the ice. This causes carbon dioxide levels to increase in the atmosphere.

C) As snow packs freeze and build up gradually over time, gases from the atmosphere are trapped within the ice and can be analyzed.

D) As snow falls onto an existing glacier, methane is released and carbon dioxide is trapped, indicating the makeup of the atmosphere at a particular time period.

Answer is C according to Usatestpep