From the question, we were told:
That the two lines are not parallel.
We are to determine how many solutions it has.
One thing we must note is that the point of intersection of a graphed equation is the solution to the graph equation.
In other words, the solution to a graph equation is the point of intersection.
From the graph given, we can see that there is only one point of intersection and that is definitely the solution to the graph.
Therefore, the number of is one.
So, the correct option is D, which is one.