Answer: The correct option is (B) The line is vertical. The slope is undefined.
Step-by-step explanation: We given to check whether the line x = 4 is horizontal or vertical.
Also, we are to find the slope of the line and select the best option.
The given line is
Since the straight line of the form x = k, a constant is parallel to Y-axis. Since Y-axis is the vertical axis, so, the line must be vertical.
Therefore, the line x = 4 is also vertical.
Now, (4, 0) and (4, 1) are any two points on the given line.
So, the slope of the line will be
which is undefined.
Therefore, the slope of the given line is undefined.
Thus, the given line is vertical and its slope is undefined.
Option (B) is correct.