I think you have misunderstood the meaning of this part of the sentence: "Obtaining water is not the least". Now let's analyze its real meaning:
the least = the one that is the lowest in rank = the least serious /the least important
NOT the least = NOT the one that is the lowest in rank = NOT the least serious = Quite serious
not the least of these problems = a quite serious problem
Of which obtaining water is not the least = obtaining water is not the least of these problems = 获取水 就是其中一个 严重 的问题
That's why you should choose A as the correct answer.
这应该是非限制性定语从句,“obtaining water ”is one of the problems, not the only problem.
所以是of which
我们有这样说的:Which of these pens do you like best? 就是用的 which of
个人认为选C
居住在澳洲中部的沙漠上还有另外的问题,不仅仅是能不能保持住水的问题。
定语从句,用AS来代前面的一句话。
obtaining water是这些problems中的一种,所以应该用表所属关系的of which.
整句话用顺序写出来就是:Living in the central Australian desert has its problems,obtaining water is not the least of these problems.
应该是A,至少我认为选A.这一题考的是非限制性定语从句.which代指前面的its problems.of which即指of its problems.即翻译为"在这些问题之中"
这是定语从句,WHICH是定物的,而且两句间有“,”所以加OF。