Match the description with the correct response. a vertical line Choose the correct answer below. A. $x+y=3$ B. $3 x-y=-10$ C. $y=-10$ D. $x=-10$

Step 1 ：Match the description with the correct response. A vertical line is represented by an equation of the form $x = c$, where $c$ is a constant. This is because for any given $x$ value, $y$ can take any value, hence the line is vertical. Therefore, the correct answer should be an equation of the form $x = c$.

Step 2 ：The correct answer is \(\boxed{D. x=-10}\).