小阻尼情况下，阻尼振动的周期为 [ ]。<br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/fe2f162d0c8b777b99a05317d1cb0316.jpg"/>. <br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/9a0196a0baf49a15abd47598ead1f20c.jpg"/><br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/00246d835c0698257b805b93cf9b86ec.jpg"/><br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/5eb3d63ec6e7453c5b1a1aa5769c93d0.jpg"/>