the correct answer is b- to be a symbol of Native Americans (It should be Americans rather than American's....this is a gramarical error! (was this from a test? the error is quite bad. with the apostrophe it refers to just one Native American. You could alternatively say of Native Americans' reclaiming of their land- a nominalisation ) reclaiming their land.
Anyway, the Alcatraz was an attempt to reclaim the Island for Alcatraz for Native Americans; and the basis for their claim to it was the treaty of 1868 in which all abandoned land was to be returned to the Native Americans (but Alcatraz wasn't).
