Final answer:
The graph of a step function consists of a series of horizontal line segments, which means the correct answer to the question is option a.
Step-by-step explanation:
Step function. These functions resemble a staircase and are also known as 'staircase functions.' They are typically used to represent situations where the function stays constant within certain intervals.
Linear functions, on the other hand, are graphed as straightforward lines that can have a positive, negative, or zero slope, corresponding to upward, downward, or horizontal lines, respectively, consistent with the provided descriptions of linear relationships. Horizontal lines are indeed a special case of linear functions where the slope (b) is equal to zero.
However, a step function is a more precise answer here, as it is characterized by multiple horizontal lines at different levels, not just a single horizontal line.
The correct answer to the question is option a. Step function.