Answer is: c. 6.02 x 10^23.
n(N₂) = 1.00 mol; amount of nitrogen molecules.
Na = 6.02·10²³ 1/mol.
Na is Avogadro number or Avogadro constant (the number of particles, in this example nitrogen molecules, that are contained in the amount of substance given by one mole).
N(N₂) = n(N₂) · Na.
N(N₂) = 1.00 mol · 6.02·10²³ 1/mol.
N(N₂) = 6.02·10²³; number of nitrogen molecules.