The correct option is B 64X
The atomic number, Z, is equal to number of protons, which is equal to number of electrons, as the atom is neutral. So, Z= 4.
Also, the mass number, A, is given as N+Z, where N is the number of neutrons. So, A=N+Z=2+4=6. And, nucleus is represented as AZX so, this nucleus is represented as 64X