Competition in the mid-nineteenth century by large western farms gradually caused farmers in Pennsylvania to turn to livestock raising, but before that it was predominantly grain-producing.

1. Competition in the mid-nineteenth century by large western farms gradually caused farmers in Pennsylvania to turn to livestock raising, but before that it was predominantly grain-producing.
2. Once predominantly a grain-producing state, competition in the mid-nineteenth century from large western farms gradually was causing Pennsylvania’s farmers to turn to livestock raising.
3. Pennsylvania’s farmers were gradually caused to turn to livestock raising by competition from large western farms in the mid-nineteenth century, but before that it was predominantly a grain-producing state.
4. It was once predominantly grain-producing, but competition in the mid-nineteenth century by large western farms was gradually causing Pennsylvania’s farmers to turn to livestock raising.
5. Pennsylvania was once a predominantly grain-producing state, but competition in the mid-nineteenth century from large western farms gradually caused the state’s farmers to turn to livestock raising.

答案是E, 没有疑问, 但是有一个问题不解.

A中的it指代不明确是没有争论的, 但是that是指代什么? 感觉似乎是在指代前面的整个句子, 但是that可以这样指代吗? 是否存在错误?

请教了!

指代前面的整个句子,  可以这样指代吧，不过OG里没有发现有

在GMAT里，凡是发现it/ that/ which/ 指代整个句子的，都是错误的。

这是GMAT的一个规则。

我的看法不同,that指代整个句子的用法,我在gmat语法里面没有见过

常用that的指代一般在比较句中的省略,除此,没有想到例子