In the 1980's the rate of increase of the minority population of the United States was nearly twice as fast as the 1970's. = In the 1980's the rate of X was ....... the 1970's = the rate of X was in the 1980's .......... rate of X was in the 1970's = the rate of X was in the 1980's .......... it was in the 1970's
(It should be like this for proper comparison) only B and C remains.
B is not proper as because rate1 .. as fast as .. rate2 not proper comparsion.. rate.. as much as... rate2 (looks ok)