I assume that the "acceleration graph" is a graph of the force versus the mass.
In such a graph, the acceleration is equal to the slope of the line, given Newton's second law:

we can see that there is a direct proportionality between F and a. So, when we triple the force, if the mass remains constant, then the acceleration will also triple, and so the slope of the line increases.
Therefore, the correct answer is:
B) The slope of the line would increase.