(c) two extra neutrons and no extra electron
12C and 14C are the two isotopes of carbon atom that have same atomic number, but different mass numbers. This means that they have same number of protons and electrons, but different number of neutrons. Therefore, 12C has 6 protons, 6 electrons and 6 neutrons, whereas 14C has 6 electrons, 6 protons and 8 neutrons.