Final answer:
The correct statements are: a horizontal line has a slope of zero; a vertical line has an undefined slope; a line that rises from left to right has a positive slope; and a line that falls from right to left has a negative slope.
Step-by-step explanation:
In evaluating the slopes of different types of lines, we need to understand that each type has unique characteristics. Firstly, a horizontal line always has a slope of zero because there is no vertical change as we move along the line; there is zero rise over any amount of run.
Contrarily, a vertical line has an undefined or infinite slope, not a slope of zero, because there is no horizontal change, leading to a division by zero which is undefined. Thirdly, a line that rises from left to right will have a positive slope, indicating that as x increases, y increases as well.
Finally, a line that falls from right to left is described as having a negative slope because as x increases, y decreases. The steeper the incline or decline of the line, the greater the absolute value of the slope, signaling a stronger relationship between x and y.