34下圖電路 由a-b 兩端點往左視入之戴維寧等效電壓 VTH 及戴維寧等效電阻 RTH 各為何?(A) VTH = 5V, RTH = 10Ω (B) VTH = 5V, RTH = 20 Ω (C) VTH = 10V, RTH = 10 Ω (D) VTH =10V,RTH = 20 Ω