Answer: Choice C
We have an expression in the form
[tex]\frac{f(x+\Delta x)-f(x)}{\Delta x}[/tex]
where the [tex]\Delta x[/tex] term is approaching 0, which is what the "lim" indicates (we're applying a limit).
Note how in [tex]f(x+\Delta x)[/tex], we effectively replace every copy of x with [tex]x+\Delta x[/tex]
Choice D is close, but it's missing the "lim" notation, so it's not 100% accurate.
