The beginning of the day is represented, on the left side of the graph. And the end of the day on the right side.
So, from the graph, we see that the number of customers increases then decreases, then remains constant during the first half of the day.
Then, it rapidly increases to its maximum value, remains constant, and then rapidly decreases in the second half of the day.
Notice that the last option says the number of customers increases and then remains constant. Since it decreases before remaining constant, the last option is incorrect.
Also, the second and third options say the number of customers increases to its maximum in the first half of the day. So, they are also incorrect.
Therefore, the only option that is a possible interpretation of the graph is the first option.