$1.$ To achieve complete combustion, an ideal mixture should contain enough $\_\_\_\_\_,$ which is often provided in excess to ensure there are no unburnt $\_\_\_$ and to minimize the production of $\_\_\_\_\_.$

A$)$ oxygen, hydrocarbons, carbon monoxide

B$)$ fuel, oxides, nitrogen

C$)$ heat, residues, sulfur dioxide

$2.$ The efficiency of a pulverized fuel burner depends significantly on the $\_\_\_\_\_,$ the size of $\_\_\_,$ and the uniformity of $\_\_\_\_\_$ distribution.

A$)$ rate of combustion, coal particles, air

B$)$ pressure levels, ash particles, heat

C$)$ color of flame, fuel droplets, gas

$3.$ Stokers are used in industrial combustion processes to feed solid fuels into the furnace with controlled $\_\_\_\_\_,$ which helps manage $\_\_\_,$ and optimize $\_\_\_\_\_.$

A$)$ timing, ash content, flame stability

B$)$ speed, heat output, air regulation

C$)$ accuracy, emissions, fuel efficiency

$4.$ Fluidized bed combustion is advantageous because it allows for low$-$temperature combustion, which reduces $\_\_\_\_\_,$ and enhances $\_\_\_,$ especially for $\_\_\_\_\_$ materials.

A$)$ nitrogen oxides, energy efficiency, sulfur$-$containing

B$)$ carbon output, speed of combustion, volatile

C$)$ fuel consumption, heat recovery, moisture$-$laden