40. 已知方程組 \left\{ \begin{array}{l} x - 2y + z = a \\ x - 9y + 5z = b \\ 2x + 3y - 2z = c \end{array} \right.，則下列哪個選項之 a，b，c 可使得該方程組有解？ (A) a = 1, b = 2, c = 3 (B) a = 4, b = 5, c = 6 (C) a = \frac{1}{6}, b = \frac{1}{3}, c = \frac{1}{6} (D) a = \frac{1}{3}, b = \frac{1}{2}, c = \frac{1}{4}