1. Write the combustion reaction

Since $CNG$ is assumed to be methane, the combustion reaction is:

$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$

2. Calculate moles of reactants

• Molar mass of methane, $CH_4 = 16\,g/mol$
• Molar mass of oxygen, $O_2 = 32\,g/mol$

So,

$n(CH_4) = \frac{100}{16} = 6.25\ mol$

$n(O_2) = \frac{208}{32} = 6.5\ mol$

3. Find the limiting reagent

From the balanced equation:

$1\ mol\ CH_4 \text{ requires } 2\ mol\ O_2$

For $6.25$ mol $CH_4$, required oxygen would be:

$2 \times 6.25 = 12.5\ mol\ O_2$

But only $6.5$ mol $O_2$ is available, so $O_2$ is the limiting reagent.

4. Calculate moles of $CO_2$ formed

From the equation:

$2\ mol\ O_2 \rightarrow 1\ mol\ CO_2$

Therefore,

$n(CO_2) = \frac{6.5}{2} = 3.25\ mol$

5. Convert moles of $CO_2$ to mass

Molar mass of $CO_2 = 44\,g/mol$

$m(CO_2) = 3.25 \times 44 = 143\,g$

6. Final answer

The amount of carbon dioxide produced is:

$\boxed{143}$

This matches the stored correct answer.