Answer: C. Real numbers from 0 to 11
The smallest x value allowed is x = 0, as shown as the leftmost point on the graph at (0,0).
The largest x value allowed is x = 11 because of the right-most point (11,100).
The domain is the set of any real number between those endpoints. We can pick any fractional or decimal number in this interval since time can be subdivided however you want, so the set of integers isn't enough.