Which of the following is a property of linear equations?

Linear equations are defined by their characteristic of being first-degree equations, which means that the highest exponent of the variable is one. This leads to the fundamental property that they graph as straight lines on a coordinate plane. The inclusion of a slope is a key feature of linear equations, as it indicates the steepness or incline of the line.

Having a slope means that for any two points on the line, there is a constant rate of change between the x-coordinates and y-coordinates, which can be described by the equation of the line in the form (y = mx + b), where (m) represents the slope and (b) is the y-intercept.

The other aspects mentioned in the options are not consistent with the properties of linear equations. Exponents greater than one would indicate a quadratic or higher-degree polynomial, while stating that they do not form straight lines contradicts the very definition of linearity. The requirement for two variables is not a necessity for linear equations; they can also exist in a single variable, such as (y = mx + b) where (y) depends on (x).