单选题 The cardinality of a finite set is the number of elements in the set．What is the cardinality of set A? (1) 2 is the cardinality of exactly 6 subsets of set A． (2) Set A has a total of 16 subsets．including the empty set and set A itself．

A、 Statement(1) ALONE is sufficient，but statement (2) alone is not sufficient．
B、 Statement(2) ALONE is sufficient，but statement (1) alone is not sufficient．
C、 BOTH statements TOGETHER are sufficient，but NEITHER statement ALONE is sufficient．
D、 EACH statement ALONE is sufficient．
E、 statements(1) and(2) TOGETHER are NOT sufficient．

【正确答案】 D

【答案解析】Let n be the cardinality of the finite set A. What is the value of n ?(1) The number of 2-element subsets of A is equal to the number of unordered selections without replacement of 2 objects from a collection of n distinct objects, or "n choose 2."Therefore, we have