33.【圖 33】之系統方塊圖，輸入為 R(s)，輸出為 Y(s)，則下列何者為系統之轉移函數 Y(s)/R(s)？(A)(G1(s)+G2(s))/[1+G3(s)(G1(s)+G2(s))] (B)G3(s)(G1(s)+G2(s))/[1+G3(s)(G1(s)+G2(s))] (C) G3(s)(G1(s)+G2(s))/[1+ (G1(s)+G2(s))] (D) G3(s) G1(s) G2(s)/[1+G3(s) G1(s) G2(s)