In the Cartesian coordinate plane, which statement correctly describes the lines that are horizontal and vertical?
A) Vertical lines have a slope of 0, and horizontal lines have an undefined slope.
B) Vertical lines have an undefined slope, and horizontal lines have a slope of 0.
C) Vertical lines have a slope of 1, and horizontal lines have a slope of -1.
D) Vertical lines have a slope of -1, and horizontal lines have a slope of 1.