Sentence Correction (SC) | Re: In the 1980’s the rate of increase of the minority population of the U

As many people correctly pointed out, B tries to modify the noun "rate" as "fast", making the sentence illogical.

In addition, B uses the pronoun "it" incorrectly. It must refer to the SAME "copy" of thing. For example:

-Mike saw a scrumptious piece of cherry pie at the shop. The temptation was too great, and he had to eat it.

Here, "it" refers to the same piece of cherry pie, Mike had seen earlier.

"it" in B refers to the same rate