【单选题】
<img src=https://huaweicloudobs.ahjxjy.cn/2F52BEA93676BA6C5C8758C754456F0B.jpg title=72-B.jpg alt=72-B.jpg/>
①
<img src=https://huaweicloudobs.ahjxjy.cn/3489A1FD33D727FB90741CD978206043.jpg title=72-1.jpg alt=72-1.jpg/>
②
<img src=https://huaweicloudobs.ahjxjy.cn/B096B0E06B9EFF5EFB58F2586F2F491E.jpg title=72-2.jpg alt=72-2.jpg/>
③
<img src=https://huaweicloudobs.ahjxjy.cn/7CBC11A8FFF66F8649DE906B99E60303.jpg title=72-3.jpg alt=72-3.jpg/>
④
<img src=https://huaweicloudobs.ahjxjy.cn/A6B68B4D2F28219C542E8C7198B7998B.jpg title=72-4.jpg alt=72-4.jpg/>
【单选题】
数据70,71,72,73的标准差是( )
①
<img class="kfformula" src="20190809/1565330298796439.png" data-latex="\sqrt {2}"/>
②
<img class="kfformula" src="20190809/1565330298960506.png" data-latex="\frac {\sqrt {5}} {2}" width="77" height="66"/>
③
<img class="kfformula" src="20190809/1565330298946541.png" data-latex="2"/>
④
<img class="kfformula" src="20190809/1565330298247161.png" data-latex="\frac {5} {3}" width="84" height="70"/>