Can someone help me to determine which of the following are isotopes please?

A. 12 electrons 12 protons 12 neutrons. B.12 electrons 12 protons 14 neutrons. C.10 electrons 11 protrons 12 neutrons. D. 10 electrons 8 protons 8 neutrons. E. 9 electrons 9 protons 10 neutrons, and can you please explain to me how you identify them thanks.