Living in the central Australian desert has its problems,___ obtaining water is not the least.

A.
生活在澳大利亚沙漠的中心要面临一些问题,其中重要的一个就是取水问题.
not least of =not the least of = a phrase used when you are giving an important reason for something,or an important example of something 部分的;尤其(用于陈述重要理由或举出重要例子)
含最高级的否定比较句最常见的就是not the least of这一结构,常译为“其中重要的一个”,
There were several reasons for dismissiqg him from his post,not the least of which was his neglect of duty．撤消他的职务的理由有几条,其中重要的一条是他玩忽职守.
LZ问的句子与以上例句句型类似.