One gram-equivalent of oxygen is 8 grams. Molar mass of atomic oxygen is 16 g/mol. Moles of atoms in 8g = 8g / 16g/mol = 0.5 moles. This is incorrect. One g-eq of oxygen atom is 8g. Number of g-atoms = 8/16 = 1/2. Number of atoms = $N_A/2$. If it refers to O₂ molecule, eq. wt. is 32/4 = 8. Moles of molecules = 8/32 = 1/4. Number of atoms = (1/4) * N_A * 2 = $N_A/2$. The answer key C suggests $N_A/4$.