Final answer:
There are an infinite number of labeled points between points B and U on the indifference curve Um.
Step-by-step explanation:
Between points B and U, there are multiple labeled points on the indifference curve Um. Given that the curve represents choices with the same level of utility, we can assume that there are an infinite number of labeled points between B and U. These labeled points would be the combinations of books and doughnuts that provide Lilly with the same level of utility as points A, B, C, and D.