$5.$ Catalytic cracking is preferred over thermal cracking due to its ability to lower $\_\_\_\_\_,$ control $\_\_\_,$ and increase the yield of $\_\_\_\_\_.$

A$)$ temperature requirements, residue formation, lighter hydrocarbons

B$)$ energy consumption, flame height, carbon deposits

C$)$ operational costs, gas emissions, heavier fractions

$6.$ In hydrocracking, high pressure and the presence of $\_\_\_\_\_$ help break down heavier crude components into lighter, more $\_\_\_$ fuels, suitable for $\_\_\_\_\_$ engines.

A$)$ hydrogen, valuable, diesel

B$)$ oxygen, stable, gasoline

C$)$ nitrogen, refined, jet

$7.$ The combustion of gas in industrial burners requires precise control over $\_\_\_\_\_,\_\_\_,$ and $\_\_\_\_\_$ to achieve optimal efficiency and minimize emissions.

A$)$ fuel flow, air mixture, ignition timing

B$)$ valve operations, pipe dimensions, burner size

C$)$ gas type, pressure settings, ambient temperature

$8.$ Excess air in combustion can lead to $\_\_\_\_\_,$ but it is necessary to prevent the formation of $\_\_\_\_\_,$ which are hazardous to human health and the environment.

A$)$ increased energy consumption, carbon monoxide and other incomplete combustion products

B$)$ reduced flame temperature, nitrogen oxides

C$)$ lower fuel costs, sulfur dioxides