系统开环传递函数为<img src="https://static.zxtiku.com/wangke/imgs/topic/f4596a5d5dddd41d0e5b6280bf3b4a1c.jpg"/>，则单位反馈的闭环传递函数为（） A. <img src="https://static.zxtiku.com/wangke/imgs/topic/0c41bc8a2ecfc90f588c3b2dbb2ed439.jpg"/> B. <img src="https://static.zxtiku.com/wangke/imgs/topic/6c12bc092b50de8f00074ea1b51386f6.jpg"/> C. <img src="https://static.zxtiku.com/wangke/imgs/topic/41201286c4591507a310220dc272f99b.jpg"/> D. <img src="https://static.zxtiku.com/wangke/imgs/topic/75e7cee9d99ef93f0d5569fcd71a25b0.jpg"/>