We first define what is a pure substance and what is a mixture. A pure substance is a compound that cannot be broken down unless a chemical reaction occurs. A mixture can be made up of different pure substances that are separated by a physical process without the need for a chemical reaction.
In this sense, gasoline is a mixture and octane is a pure substance. Since we are asked about the octane, we can discard the answers that tell us that it is a mixture.
Now, when a pure substance is formed by a chemical reaction, the substance that is formed has properties that are not equivalent to the properties of the atoms that form it. In other words, this new substance acquires its own characteristics, so the octane made up of hydrogen and carbon will not have the properties of these atoms, they will have different properties.
Therefore, the answer will be:
C It is a mixture containing properties different from those of hydrogen and carbon.
