Which of the following best describes the appearance of a slope field for any differential equation of the form dxdy=f(x) where the right–hand side depends only on x?
a) Slopes depend only on the product xy, so contours of equal slope are hyperbolas.
b) All line segments on any vertical line share the same slope value.
c) All line segments on any horizontal line share the same slope value.
d) Slopes are zero along the line y=x and change sign across that line.