$ = \frac{{16}}{{48}} \times 6.023 \times {10^{23}}$ molecules

$ = 3 \times \frac{{16}}{{48}} \times 6.023 \times {10^{23}}$ atoms

$= 6.023 \times 10^{23}$ atoms

$28.0\,g\,CO = \frac{{28}}{{28}}$ mole $= 1$ mole

$ = 1 \times 6.023 \times {10^{23}}$ molecules

$ = 1 \times 6.023 \times {10^{23}}$ atoms

$ = 6.023 \times {10^{23}}$ atoms

$16.0\,g\,{O_2} = \frac{{16}}{{16}}$ mole $= 1$ mole

$ = 1 \times 6.023 \times {10^{23}}$ molecules

$ = 1 \times 6.023 \times {10^{23}}$ atoms

$ = 6.023 \times {10^{23}}$ atoms

Therefore, the ratio is

$6.023 \times {10^{23}}:6.023 \times {10^{23}}:6.023 \times {10^{23}}$

i.e. $1:1:1$