Why did the whig party choose william henry harrison over henry clay for the election in 1840?

How should the student cite this source using mla citation format?

Why might collective bargaining fail, causing a union to go on strike? a the union agrees with the boss about wages. b the boss compromises about work hours. c the factory goes out of business, causing the workers to lose their jobs. d the boss refuses to address dangerous working conditions in the factories.

Which piece of information would most a historian create an interpretation of this photograph of works in a factory?