答案：D

解析：

If the graph of the function , which contains the points (0,-9) (1,-4) and (3,0) were a line, then the slope of the segment connecting the points (0,-9) and (1,-4) would be the same as the slope of the segment connecting the points (1,-4) and (3,0). However, the slope of the segment connecting the points (0,-9) and (1,-4) is 5, and the slope of the segment connecting the points (1,-4) and (3,0) is 2. Therefore, the graph of f cannot be a line.

The statements in the other four options could be true. For example, if the equation of f were y=-(x-3)(x-3), then the graph of f would contain the points (0,-9),(1,-4) , and (3,0). The graph of f would be a parabola symmetric with respect to the line with equation x=3. The maximum value of f would occur at the point (3,0), and y<=0 would be true for all points (x,y) on the graph of f.