Answer:
The graph increases if the line goes upwards. (The end of the segment is above the start of the segment)
The graph decreases if the line goes downwards. (The end of the segment is below the start of the segment)
The graph is constant if the line is horizontal. (The end of the segment is at the same height as the start of the segment)
Then:
The graph of the function is increasing in the segments c and e.
The graph of the function is decreasing in the segments a and f.
The graph of the function is constant in the segments b and d.