$(a)$ Classify the two fuels, $CNG$ and hydrogen, as renewable and non-renewable.
$(b)$ Justify the statement, "Hydrogen is a cleaner and better fuel than $CNG$."

(N/A) $CNG$ is a non-renewable source of energy because it is a fossil fuel that takes millions of years to form and is present in limited quantities.
Hydrogen is a renewable source of energy because it can be produced from water through electrolysis and is virtually inexhaustible.
$(b)$ Hydrogen is considered a cleaner and better fuel than $CNG$ because:
$1$. Hydrogen combustion produces only water $(H_2O)$ as a byproduct, which is environmentally harmless.
$2$. $CNG$ combustion produces carbon dioxide $(CO_2)$, which is a greenhouse gas contributing to global warming, although it produces less pollution than coal or petroleum.