单选题：Given S = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 } and 8 equivalen

Given S = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 } and 8 equivalence relations: 5\~6，7\~8，9\~10，2\~6，3\~8，6\~8，1\~8，1\~5. After invoking successively these relations with union-by-size（if the two sizes are equal, the smaller element will be the root）and path compression, which one of the following statements is false?
@[C](3)

A. there are 4 equivalence classes
B. element 1 is a child of element 5
C. all elements are either a root or a child of a root
D. element 2 and element 8 are siblings



A.there are 4 equivalence classes
B.element 1 is a child of element 5
C.all elements are either a root or a child of a root
D.element 2 and element 8 are siblings


答案：C