A. I1R1+I2R2+l3R3+14R4=US1+US2+US3 B. I1R1+I2R2-l3R3-14R4=US1+US2+US3 C. I1R1+I2R2-l3R3-14R4=US1-US2-US3 D. I1R1-I2R2-l3R3+14R4=US1-US2-US3