In order to identify the function that better decribes the graph, you consider that you have two lines in two intervals.
In the first line the interval is in between [0,2) , right limit is an open parenthesis becasue in the graph you have a blank point, which means that the point is not included. Right limit is a closed parenthesis because x = 0 is included in the interval.
In the second line the interval is in between [2,4)
The first line is y = x
the second line is y = x - 2
Hence, the answer is A.
