In complete combustion of fuels lead to formation of . 1. carbon monoxide
2. carbon dioxide
3. chlorofluorocarbon
4. hydrogen sulphide ​

Explanation:

Complete combustion reacts oxygen with a fuel to produce carbon dioxide and water. Because the air we breathe is only 21% oxygen, a large volume of air is required for complete combustion to take place. Combustion is an exothermic reaction that releases energy in the forms of heat and light.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.