Moreover, it is unclear how groups should be classified that are hunter-gatherers in their procurement strategies but that make use of pastoralism and cultivation in their consumption patterns——subsisting.

【分析】句子总体是一个“主系表”结构。

1. it（形式主语） is （系动词）unclear （表语） how groups should be classified （真正主语）

2. that are hunter-gatherers in their procurement strategies but that make use of pastoralism and cultivation in their consumption patterns （两个转折意义的定语从句，修饰groups）

3. 此现象属于“词语分隔或成分分隔”。因定语过长，为保持句子匀称，将两个定语从句后移，与先行词分离开来。分隔的成分是 should be classified。分隔类型是：定语从句与先行词被分隔。又如：

He laughs best who laughs last.

谁笑到最后，谁笑得最好

All are not friends that speak us fair.

说我们好话的未必都是朋友。

What have you done that upset her?

你做了什么让她不高兴的事?

The days are gone when we Chinese were bullied by the invaders.

我们中国人被侵略者欺凌的日子一去不复返了。

The village has developed a lot where we learned farming two years ago.

这个村庄发展很快，两年前我们在那里学习种植。