Bohr explains that the atom consists of a nucleus which contains protons and neutrons in it and electrons revolve around the nucleus in different orbits. The nucleus is positively charged and electrons revolving around are negatively charges.
According to Bohr's model of atom, there are different number of shells in which electrons revolve. The shells are named as K, L, M, N... According to Bohr's model, K shell which is lowest shell can only have two electrons in its orbit. Therefore, Bohr's model shown in 1. is correct as it has only two electrons in K shell.