信号<img src="https://static.zxtiku.com/wangke/imgs/topic/2a6f71147d629556d41f305dcdd9cf90.jpg"/>，其功率谱密度为（）。<br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/17f931fc9d4b23217616b6e7197f657c.jpg"/><br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/626aa396f327ee55e7669b3da54f1dd8.jpg"/><br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/4df509c77cf028bacda6cbc30a2ce13f.jpg"/><br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/cb2f300dd6e8ae2f6b7cd59f98a02bdf.jpg"/>