对于函数<img src="/lqwvjeImg/e0/e012820946422ee78dd2949888662a4c.png"style="width:45px;height:24px;">,下列结论正确的是( )<br>· <img src="/lqwvjeImg/a0/a0d176744d6a73640dac768976913091.png"style="width:37px;height:18px;">是极小值点<br>· <img src="/lqwvjeImg/1e/1e3f4e6de4e4df01a706107af4fff672.png"style="width:38px;height:18px;">是极大值点<br>· <img src="/lqwvjeImg/80/80f5bf59645be35ca78254e58b896402.png"style="width:35px;height:21px;">是曲线的拐点<br>· <img src="/lqwvjeImg/80/80f5bf59645be35ca78254e58b896402.png"style="width:35px;height:21px;">不是曲线的拐点