Final answer:
The line containing the points (−7, 5) and (−7, −9) is vertical, as it has the same x-coordinates and different y-coordinates.
Step-by-step explanation:
To determine whether the line containing the points (−7, 5) and (−7, −9) is horizontal, vertical, or neither, we look at the x and y coordinates of both points. A horizontal line will have the same y-coordinates and different x-coordinates, while a vertical line will have the same x-coordinates and different y-coordinates.
Since both points have the same x-coordinate (−7) and different y-coordinates (5 and −9), we can conclude that the line is vertical. Therefore, the answer to the student's question is b. Vertical. It doesn't matter whether the line is considered to extend vertically upward or downward in the coordinate system, as vertical lines have an undefined slope and don't have a direction associated with them.