Which choice fits in the blank in this progressive era timeline? a.1903- helen hunt jackson publishes regarding treatment of native americans b.1906- upton sinclair publishes the jungle, criticizing the working conditions in the u. s. meat processing industry eliminate c.1912- theodore roosevelt publishes the square deal in which he addresses problems in the treatment of american unions d.1912- sir arthur conan doyle publishes the lost world showing the deforestation of the rain forests?