Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

[EX Q]: With which song did Swedish pop group Abba win the 1974 Eurovision Song Contest?
[EX A]: abba

[EX Q]: The Church of the Savior on Spilled Blood, built on the site of the assassination of Tsar Alexander II, is in which Russian city?
[EX A]: church of the savior on blood

[EX Q]: By what name was Barbara Gordon known in DC Comics from 1967 to the mid-1980s?
[EX A]:
barbara gordon