单选题 S is a set of integers such that
i) if a is in S. then -a is in S, and
ii) if each of n and b is in S, then ab is in S. Is -4 in S?
(1)1 is in S.
(2)2 is in S.
(A) 条件(1)充分，但条件(2)不充分．
(B) 条件(2)充分，但条件(1)不充分．
(C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
(D) 条件(1)充分，条件(2)也充分．
(E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．