The answer to this is 6,6. There is sometimes a need for electrons and protons to be equal when the given atom is neutral in charge. An atom has three atomic particles. The first one is the proton which has a positive charge. The second one is the electron which has a negative charge, and lastly, there is the neutron which does not have any charge.
For this particular question, A is the right answer because of the given atomic number. The atomic number is 12 which means that it is the sum of both the protons and the electrons that are present. If the other choices would be added, the atomic number would be too much. It is only A that will give the sum of 12.