如图所示系统总的传递函数G(s)=C(s)/R(s) 应为（）。<img src="https://static.zxtiku.com/wangke/imgs/topic/2b92dc5e61f9e782fe7296b435a65c5f.jpg"/> A. <img src="https://static.zxtiku.com/wangke/imgs/topic/c4f0bf0c06e548ebfd4880302b37f741.jpg"/> B. <img src="https://static.zxtiku.com/wangke/imgs/topic/9ef146e131cdaeb82991e49ea2b73e2f.jpg"/> C. <img src="https://static.zxtiku.com/wangke/imgs/topic/da5e4aae9411378051562a9429f5be75.jpg"/> D. <img src="https://static.zxtiku.com/wangke/imgs/topic/d02f2605783f0a731362db9fc6b352a1.jpg"/>