Final answer:
Trinity College Meeting is the oldest democratically elected student government in Canada, predating other listed options and established in 1858.
Step-by-step explanation:
The oldest democratically elected student government in Canada is Trinity College Meeting. Established in 1858, this body predates the other listed organizations and governs at Trinity College within the University of Toronto. Student governments like these play a crucial role in representing student interests, similar to how the Students for a Democratic Society (SDS) aimed to involve ordinary people in the democratic process in the United States during the 1960s. While SDS was not directly linked to student governments in Canadian universities, the spirit of activism and democratic participation in educational institutions is a shared theme.