Can someone help me answer this question? Apparently it's' not A
The graph shows the production of cars per day at a factory during a certain period of time. What is the domain of this function during this period?

Graph of days versus cars. Points are plotted at the following coordinates: 0 comma 0, 1 comma 50, 2 comma 100, 3 comma 150, 4 comma 200, 5 comma 250, 6 comma 300, 7 comma 350, 8 comma 400, 9 comma 450.

The domain is all real numbers 0 through 9.

The domain is all integers 0 through 9.

The domain is all positive real numbers.

The domain is all positive integers.

Question

Can someone help me answer this question? Apparently it's' not A
The graph shows the production of cars per day at a factory during a certain period of time. What is the domain of this function during this period?

Graph of days versus cars. Points are plotted at the following coordinates: 0 comma 0, 1 comma 50, 2 comma 100, 3 comma 150, 4 comma 200, 5 comma 250, 6 comma 300, 7 comma 350, 8 comma 400, 9 comma 450.

 The domain is all real numbers 0 through 9.

 The domain is all integers 0 through 9.

 The domain is all positive real numbers.

 The domain is all positive integers.