若A为6阶方阵，齐次方程组Ax=0基础解系中解向量的个数为2， 则（ ）。\n \n \n \n \n \n \n

\n \n \n \n A.\n 2\n

\n \n

\n \n \n \n B.\n 3\n

\n \n

\n \n \n \n C.\n 4\n

\n \n

\n \n \n \n D.\n 5\n