- In the 1980’s the rate of increase of the minority population of the United States was nearly twice as fast as it was in the 1970’s.
- 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.
- In the 1980’s the rate of increase of the minority population of the United States was nearly two times faster than that of the 1970’s.
- In the 1980’s the rate of increase of the minority population of the United States was nearly two times greater than the 1970’s.
Can anyone explain correct grammatical sentence between these ?