极限 <img src="https://static.zxtiku.com/wangke/imgs/topic/48897b2a33acdb098c9b1f1073222feb.jpg"/>存在的充要条件是（）.<br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/a3b5f5672fe87c489b6ee1932a76b295.jpg"/><br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/e0e5861b6d57539f37adf5dc22b74d5a.jpg"/>存在<br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/fb2c1cfaa865f296dbef295173728bf8.jpg"/>存在<br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/ed6e28f477146edeaf580ac75f0257c2.jpg"/>与<img src="https://static.zxtiku.com/wangke/imgs/topic/eb6ec5c559082cf8f98ba7935c576b17.jpg"/>存在且相等