In the graph the points are connected by the straight lines, so graph is linear graph. In nonlinear graph the points are connected by the curve. So option A is incorrect.
The slope of the line changes after x=2. The inclination of line with positive x axis is different before and after x=2. So the function not increases at same rate. Then option B is incorrect.
The rate is given by the slope of line. The inclination of line with positive x axis increase after x=2, so rate increases not decreases. Then option C is incorrect.
The graph of a straight line is function or not a function can be inspected by vertical line test.
If we draw a vertical line, then the vertical line intersect the line only once, so the graph is function. Option D is correct.
The value of y increases with increase in value of x but increase in value of y with x is different for two lines. So graph is increasing in two intervals. Option E is also correct.
Thus option D and E is only true for given graph.