The correct answer is option 3, C.

To determine who saves the least percentage of their monthly income, we need to look at the graph provided. If we analyze the bars representing the savings of each person, we can see that person C has the smallest bar, indicating the least amount of savings. Therefore, person C saves the least percentage of their monthly income compared to persons A, B, and D.

It is important to note that the graph does not provide exact values for the savings of each person, but rather a visual representation of the savings. Therefore, we can only determine the relative amount of savings between the individuals based on the graph.

It is always a good practice to carefully analyze the given options and refer to the provided information or data when answering questions like these.