以下结论正确的是( )<br>·函数<img src="https://zk.995w.com/lqwvjeImg/4e/4e89b6afb4642f5407db06cda89a8ccc.png"style="width:36px;height:21px;">的导数不存在的点,一定不是的极值点<br>·若<img src="https://zk.995w.com/lqwvjeImg/f1/f16d98626de591961eea75a683ac37a6.png"style="width:18px;height:24px;">为函数的驻点,则<img src="https://zk.995w.com/lqwvjeImg/f1/f16d98626de591961eea75a683ac37a6.png"style="width:18px;height:24px;">必为<img src="https://zk.995w.com/lqwvjeImg/4e/4e89b6afb4642f5407db06cda89a8ccc.png"style="width:36px;height:21px;">的极值点<br>·若函数<img src="https://zk.995w.com/lqwvjeImg/4e/4e89b6afb4642f5407db06cda89a8ccc.png"style="width:36px;height:21px;">在<img src="https://zk.995w.com/lqwvjeImg/f1/f16d98626de591961eea75a683ac37a6.png"style="width:18px;height:24px;">处有极值,且<img src="https://zk.995w.com/lqwvjeImg/53/53b36ff20909f7b85565c2057daaa869.png"style="width:48px;height:25px;">存在,则必有<img src="https://zk.995w.com/lqwvjeImg/86/866092c5546d967e8dde5d3624a6f3cf.png"style="width:72px;height:25px;"><br>·若函数<img src="https://zk.995w.com/lqwvjeImg/4e/4e89b6afb4642f5407db06cda89a8ccc.png"style="width:36px;height:21px;">在<img src="https://zk.995w.com/lqwvjeImg/f1/f16d98626de591961eea75a683ac37a6.png"style="width:18px;height:24px;">处连续,则<img src="https://zk.995w.com/lqwvjeImg/53/53b36ff20909f7b85565c2057daaa869.png"style="width:48px;height:25px;">一定存在