IMO , C should be the answer y ??
That is required in the beginning to ensure parallelism.
so A and B wrong.
E wrong because anidiscrmination ... is singular
D wrong because mitigated should modify inequity and not housing practice's..
Please correct me if i am wrong
Agencies studying discrimination in housing have experimentally proved that minority clients are often discouraged as prospective buyers of residential real estate and the antidiscrimination legislation of recent decades were only mitigating, rather than abolishing, inequity in housing practices.
(A) the antidiscrimination legislation of recent decades were only mitigating, rather than abolishing, inequity in housing practices
(B) in recent decades, the antidiscrimination legislation only mitigated, rather than abolishing, inequity in housing practices
(C) that antidiscrimination legislation of recent decades has only mitigated, rather than abolished, inequity in housing practices
(D) that, in recent decades, antidiscrimination legislation has only mitigated, rather than abolishing, housing practices' inequity
(E) that recent decades' antidiscrimination legislation only were mitigating, rather than abolishing, housing practices' inequity