,
,
,则
( )。\n \n \n \n \n \n \n \n \n \n \n A.\n 6 \n
\n \n\n \n \n \n B.\n -4 \n
\n \n\n \n \n \n C.\n -2 \n
\n \n\n \n \n \n D.\n 4\n