The correct answer is C. I and II.

Explanation: The term $f(x)$ represents the value of the function $f$ at a particular point $x$. This is often referred to as the value of $f$ at $x$, and it is also the image of $x$ under $f$. Both statements I and II correctly describe $f(x)$.

Would you like further details on function notation?

Here are five related questions:

1. What is the difference between a function's domain and range?
2. How do we interpret the notation $f(a) = b$?
3. What does it mean if $f(x) = g(x)$ for all $x$ in a certain interval?
4. How can we determine if a function is one-to-one?
5. What is the significance of the inverse of a function?

Tip: Always check if a function is well-defined for all elements in its domain to avoid undefined values.