Circle A has radius 100 . Circle B has an integer radius r<100 and remains internally tangent to circle A as it rolls once around the circumference of circle A. The two circles have the same points of tangency at the beginning and end of circle B 's trip. How many possible values can r have?

**Answer Choices**

A. 4

B. 8

C. 9

D. 50

E. 90