The correct answer is A. 0.
A neutral copper atom has 29 protons, 29 electrons, and 29 neutrons. The number of protons in the nucleus of an atom determines the element’s atomic number, which is 29 for copper. The number of electrons in an atom is equal to the number of protons in the nucleus, so a neutral copper atom has 29 electrons. The number of neutrons in the nucleus of an atom can vary, and this variation is what gives rise to isotopes of an element. Copper has two naturally occurring isotopes, copper-63 and copper-65. Copper-63 has 34 neutrons and copper-65 has 36 neutrons.
The net charge of an atom is equal to the number of protons minus the number of electrons. Since a neutral copper atom has 29 protons and 29 electrons, the net charge is 0.