What Was the Advantage of Looking for DNA Samples in Permafrost

What was the advantage of looking for DNA samples in permafrost?

A) Most plants and animals evolved in Siberia
B) It is easier to take solid core samples
C) The enzymes that make DNA are still active in the cells
D) The freezing temperatures preserves the DNA
E) Areas with permafrost are older than other parts of the world, allowing scientists to collect samples back 1.5 to 2 million years