下列梯度计算公式正确的是<br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/9df00723e96959a06cdaf5130a432750.jpg"/><br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/87e3c1ff4826bd536001bedf69402bbb.jpg"/><br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/8d1a7c576c4f083a05424920d578779b.jpg"/><br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/1055c2609dfdc68e2d0b6a76c6823ed7.jpg"/>