Solution:
The rate of change of a graph is the same as the slope of the graph.
The graph that has a rate of change of 1/2 is the graph with a slope of 1/2.
To calculate the slope of a graph,
Considering two clear points from graph C, picking the points (2,-1) and (4,0)
Therefore, the graph that represents a rate of change of 1/2 is the graph of option C.