32. 下列電路圖中,其 I1 網目之電流方程式應為何? (A) 7I1 – 4I2 – 3I3 = 22 (B) 7I1 – 4I2 – 3I3 = 18 (C) 7I1 – 4I2 – 3I3 = -20 (D) 7I1 – 4I2 – 3I3 = 20