关于ｉｔ指代的问题一个题目。白勇上的

5.in the 1980's the rate of increase of the minority population of the United States was nearly twice what it was in the 1970's.

这是改过后的句子。有点疑问。it不是用来指代同一个东西吗？那么rate 在1980与1970是同一个东西吗？不应该是that才对吗？  请大家指教。

我也觉得不要it更好 等斑竹们来解答一下

帮顶

In A.D. 391, as s result of the destruction of the library
            at Alexandria,
                the largest
                of the
ancient world, later generations lost all but
the Iliad and Odyssey among Greek epics, most of the poetry of Pindar and
Sappho, and dozens of plays by Aeschylus and Euripides.