问题
1-2+3-4+5-6+7-8+…+1989-1990+1991=______。
A.895
B.896
C.995
D.996
Fatal error: Uncaught [XSException] ../../../usr/local/xunsearch/sdk/php/lib/XS.php(2559): Connection refused(C#111, localhost:8384)
thrown in /usr/local/xunsearch/sdk/php/lib/XS.php on line 2559