下列给定区间中是函数<img src=https://huaweicloudobs.ahjxjy.cn/9F41F2144F77B9734834D11F298AE76E.png style=vertical-align: middle;/>的单调有界区间的是
①
<img src=https://huaweicloudobs.ahjxjy.cn/4E0D2D6A0B16D558EB614EF772580355.png style=vertical-align: middle;/>
②
<img src=https://huaweicloudobs.ahjxjy.cn/BE5F5EE234FE689F6670A1882D989361.png style=vertical-align: middle;/>
③
<img src=https://huaweicloudobs.ahjxjy.cn/6CA414105ADBB59F6207CC8A54CE6FC7.png style=vertical-align: middle;/>
④
<img src=https://huaweicloudobs.ahjxjy.cn/B74AF5DE9991AB21FC087659C071C406.png style=vertical-align: middle;/>