Why are Carbon-14 and carbon-12 considered to be isotopes?
A. Carbon-14 decays at a faster rate that Carbon-12
B. Carbon-14 is more stable than Carbon-12.
C. Carbon-14 has more neutrons than carbon-12.
D. Carbon-13 is roughly 2 any heavier than Carbon-14.
E. Both atoms have six protons in the nucleus, but have different atomic masses.