Final answer:
Among the provided statements, only A) Horizontal lines have a slope of 0 is true, as horizontal lines run left to right with no rise. Vertical lines have an undefined slope, not a slope of 0 or 1.
Step-by-step explanation:
Among the statements about horizontal and vertical lines, A) Horizontal lines have a slope of 0 is true. When you look at a graph, a horizontal line runs left to right and does not rise or fall, thus it has a slope of zero. On the other hand, answer D suggests that vertical lines have a slope of 0, which is incorrect; vertical lines have an undefined slope, reason being you cannot divide by zero, which would be the case with the rise over run calculation for slope in vertical lines.
So, the correct statements from the options are: A) Horizontal lines have a slope of 0, and it's also important to note that while B) is incorrect as vertical lines do not have a slope of 1, they rather have an undefined slope due to the division by zero as mentioned before. Therefore, C) is incorrect as horizontal lines do indeed have a defined slope which is zero, not undefined.