In the case of reed v. Reed from 1971, how did the US supreme court curb gender discrimination

A. By arguing for women's right to privacy in their own healthcare decision
B. By urging the senate and house of representatives to ratify the equal rights amendment
C. By ruling out arbitrary gender classification with the equal protection clause
D. By mandating gender based affirmative action policies in the public sector

C. By ruling out arbitrary gender classification with the equal protection clause