Stones are numbered 1,2,3,4,5,6,7,8,9,10. Three groups of stones can be selected so that the sum of each group is 11. For example, one arrangement is${1,10},{2,3,6},{4,7}$. Including the example, how many arrangements are possible?
Answer Choices
A. 13
B. 16
C. 11
D. 12
E. 15