The correct answer is Choice D.
Knowing that function $f(x)$ is linear, it can be written in the slope-intercept form $f(x)=mx+b$, where $m$ is the slope and $b$ is the $y$-intercept.
Choice A is incorrect because a function that is constant is horizontal.
Choice B is incorrect because the function passes the origin, not having a $y$-intercept of $(0,-2)$.
Choice C is incorrect because the slope should be negative since the value of $y$ decreases and $x$ increases.
✨ Expert's Tip ✨
An alternate method is to plot graphs for each of the four functions and read the values at $x=-2$ and $x=0$ for verification.