题目1单选题
关于曲线<img src="https://tihai-oss-cloud.itihey.com/img/ec45b8717b80a1e6a6d6aebf4bb89ac9.png">,下列说法正确的是( )A. 在<img src="https://tihai-oss-cloud.itihey.com/img/e1ceb3801c1aa671a8d343ea348216f2.png"> 上是凸的B. 在<img src="https://tihai-oss-cloud.itihey.com/img/e1ceb3801c1aa671a8d343ea348216f2.png"> 上凹的C. 在<img src="https://tihai-oss-cloud.itihey.com/img/e1ceb3801c1aa671a8d343ea348216f2.png"> 上有拐点D. 在<img src="https://tihai-oss-cloud.itihey.com/img/e1ceb3801c1aa671a8d343ea348216f2.png">没有凹凸性