题目1单选题
函数 <img src="https://tihai-oss-cloud.itihey.com/img/957f7377cbbe45ac03086e4283b648bd.png"> 在点 <img src="https://tihai-oss-cloud.itihey.com/img/7a85045064921421d97678ba6f129da8.png"> 处的梯度是A. <img src="https://tihai-oss-cloud.itihey.com/img/ff7e7d405f6f650ca7c2e68e706be7c8.png">B. <img src="https://tihai-oss-cloud.itihey.com/img/315e4bd2ac589db109aa34fed130e6de.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/2606de6030b2097c2d7d6d0631442ba8.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/a68828a51b7c9a5c80bd6aa6a0f1b5d1.png">