Step 1: Concept
An oxidising agent gets reduced itself. The species with the highest (most positive) standard reduction potential is the strongest oxidising agent.
Step 2: Analysis
- Fluorine ($F_2$) has the highest reduction potential in the electrochemical series ($+2.87\text{ V}$).
- It has a very high tendency to accept electrons to form $F^-$.
Step 3: Conclusion
$F_2$ is the strongest oxidising agent, while $Li$ (metal) is the strongest reducing agent.
Final Answer: (C)