Which of the following statements is true? O A neutral Mg atom having electron configuration [Ne]4s? cannot emit photons. O The 1s electrons of a carbon atom shield its 2s electrons better than they shield its 2p electrons. O A neutral oxygen atom in its ground state has two unpaired electrons. O The subshells of the n = 4 shell of a chlorine atom are degenerate, i.e. they are of the same energy, because those orbitals don't have any electrons in them. O Four lines are seen in the emission spectrum of hydrogen because hydrogen has only four possible electronic transitions.