Let W($n$) and A($n$) denote respectively, the worst case and average case running time of an algorithm executed on an input of size $n$. Which of the following is ALWAYS TRUE?

By definition, the worst-case running time $W(n)$ represents the maximum time taken by the algorithm over all possible inputs of size $n$, while the average-case running time $A(n)$ represents the expected running time over a probability distribution of inputs of size $n$.

Since the average cannot exceed the maximum for any input of size $n$:

Hence, $W(n)$ is an asymptotic upper bound for $A(n)$:

Therefore, option C is always true.