49. 下圖所示數位傳輸閘邏輯網路,R=5 kΩ,下列敘述,何者正確? (A)當 S =1,輸出Y = A ⊕ B (B)當 S =0,輸出Y = A ⊕ B (C)當 S =0,輸出Y = A + B (D)當 S =1,輸出Y = A + B