<img src="https://static.zxtiku.com/wangke/imgs/topic/8998603dfbf69a44bb694e546a59085f.jpg"/><br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/437c56bfb7b400a258e2a14d6a08a59b.jpg"/>x(n) <br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/5cd71bb008b02b6cb18114f31f8f5f46.jpg"/>x(n) <br/> C、lx(n) <br/> D、N x(n)