Answer:
Harvey Milk ran for the San Francisco Board of Supervisors in 1975 and 1977. He lost in 1975 when supervisors were elected by and represented (a) ___eleven single-member districts___, but won in 1977 when San Francisco changed its institutional rules and supervisors were elected by and represented (b) ____at large (all running ballot).___.
Explanation:
Before 1978, supervisors were elected by eleven single-member districts. This District members were responsible for electing a new ‘supervisor’
From 1978 onward supervisors were elected at-large( the use of elections), with all candidates running on one ballot, this meant the candidate with top votes won unlike when members from district decided their fates, here the people were allowed to vote for their preferred candidates.