题目3单选题
设函数 <img src="https://tihai-oss-cloud.itihey.com/img/96ee10f45de88982f45a3b8d15c43d77.png">在点 <img src="https://tihai-oss-cloud.itihey.com/img/5499488bad46677b1ca2ab72754eb5b6.png">的某邻域内有连续的二阶偏导数,且 <img src="https://tihai-oss-cloud.itihey.com/img/9e708c82e31741578f0e70de342fcfe5.png">, <img src="https://tihai-oss-cloud.itihey.com/img/241a8536cac4df8887934383e74fbd2c.png">, <img src="https://tihai-oss-cloud.itihey.com/img/4d49fabd399271c9e89472594c4fbc01.png">, <img src="https://tihai-oss-cloud.itihey.com/img/a83635bdbf9adbaa4b1b5724279e87c5.png">,则在点 <img src="https://tihai-oss-cloud.itihey.com/img/5499488bad46677b1ca2ab72754eb5b6.png">的某邻域内,( )A. 由 <img src="https://tihai-oss-cloud.itihey.com/img/53f8576e9e95718e6be94131169c0f83.png">可确定函数 <img src="https://tihai-oss-cloud.itihey.com/img/be2ca3eda54c3fa663541ed4149f4410.png">,且 <img src="https://tihai-oss-cloud.itihey.com/img/be2ca3eda54c3fa663541ed4149f4410.png">在点 <img src="https://tihai-oss-cloud.itihey.com/img/a9545f7e60887de5c5ed3398dd8157ac.png">处取极大值B. 由 <img src="https://tihai-oss-cloud.itihey.com/img/53f8576e9e95718e6be94131169c0f83.png">可确定函数 <img src="https://tihai-oss-cloud.itihey.com/img/f80db68ac441c87b4c56d2ead73adaab.png">,且 <img src="https://tihai-oss-cloud.itihey.com/img/f80db68ac441c87b4c56d2ead73adaab.png">在点 <img src="https://tihai-oss-cloud.itihey.com/img/4496594bb6f791c6872c9ba04d2d3dab.png">处取极大值C. 由 <img src="https://tihai-oss-cloud.itihey.com/img/53f8576e9e95718e6be94131169c0f83.png">可确定函数 <img src="https://tihai-oss-cloud.itihey.com/img/be2ca3eda54c3fa663541ed4149f4410.png">,且 <img src="https://tihai-oss-cloud.itihey.com/img/be2ca3eda54c3fa663541ed4149f4410.png">在点 <img src="https://tihai-oss-cloud.itihey.com/img/a9545f7e60887de5c5ed3398dd8157ac.png">处取极小值D. 由 <img src="https://tihai-oss-cloud.itihey.com/img/53f8576e9e95718e6be94131169c0f83.png">可确定函数 <img src="https://tihai-oss-cloud.itihey.com/img/f80db68ac441c87b4c56d2ead73adaab.png">,且 <img src="https://tihai-oss-cloud.itihey.com/img/f80db68ac441c87b4c56d2ead73adaab.png">在点 <img src="https://tihai-oss-cloud.itihey.com/img/4496594bb6f791c6872c9ba04d2d3dab.png">处取极小值