Which answer best describes what is happening in the following reaction?

[tex]\[2 C_8H_{18} + 25 O_2 \longrightarrow 16 CO_2 + 18 H_2O\][/tex]

A. This is not a redox reaction. It is an example of combustion.
B. This is a redox reaction in which octane $\left(C_8H_{18}\right)$ is the reducing agent.
C. This is a redox reaction in which carbon dioxide $\left(CO_2\right)$ burns due to ignition.
D. This is not a redox reaction, because a solution of carbon dioxide and water results.

Let's analyze the given chemical reaction:

[tex]\[ 2 \text{C}_8 \text{H}_{18} + 25 \text{O}_2 \longrightarrow 16 \text{CO}_2 + 18 \text{H}_2 \text{O} \][/tex]

### Step-by-step breakdown:

1. Identify the type of reaction:
- The reaction given is a combustion reaction, as it involves a hydrocarbon (octane, $\text{C}_8\text{H}_{18}$) reacting with oxygen ($\text{O}_2$) to produce carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$).

2. Check if it's a redox reaction:
- A redox (reduction-oxidation) reaction involves the transfer of electrons where the oxidation states of atoms change.

3. Determine the oxidation states of elements in the reactants and products:
- For $\text{C}_8\text{H}_{18}$:
- Carbon in hydrocarbons generally has an oxidation state of $-3$ because hydrogen is $+1$.
- For $\text{O}_2$:
- The oxidation state of the oxygen molecule ($\text{O}_2$) is $0$ because it's in its elemental form.
- For $\text{CO}_2$:
- Carbon in $\text{CO}_2$ has an oxidation state of $+4$ because oxygen is $-2$.
- For $\text{H}_2\text{O}$:
- Hydrogen is $+1$ and oxygen is $-2$.

4. Determine changes in oxidation states:
- Carbon in $\text{C}_8\text{H}_{18}$ goes from $-3$ (in $\text{C}_8\text{H}_{18}$) to $+4$ (in $\text{CO}_2$). This is an increase in oxidation state, meaning carbon is being oxidized.
- Oxygen in $\text{O}_2$ goes from $0$ (in $\text{O}_2$) to $-2$ (in $\text{CO}_2$ and $\text{H}_2\text{O}$). This is a decrease in oxidation state, meaning oxygen is being reduced.

5. Identify the reducing and oxidizing agents:
- The substance that is oxidized (losing electrons) is the reducing agent.
- Here, the carbon in $\text{C}_8\text{H}_{18}$ is oxidized, making $\text{C}_8\text{H}_{18}$ the reducing agent.

### Conclusion:

The given reaction is indeed a redox reaction because there is a transfer of electrons as seen from the changes in oxidation states. The correct description of what is happening is:

[tex]\[ \text{This is a redox reaction in which octane ($\text{C}_8\text{H}_{18}$) is the reducing agent.} \][/tex]

Thus, the best answer is:

[tex]\[ \text{This is a redox reaction in which octane ($\text{C}_8\text{H}_{18}$) is the reducing agent.} \][/tex]