Why Isn't a Labor Union or a Corporation Considered to Be

Why isn't a labor union or a corporation considered to be a part of the government?

A) Labor unions and corporations do not have elected officials.
B) Labor unions and corporations cannot enforce rules for all of society.
C) Labor unions and corporations cannot create any legitimate rules.
D) Labor unions and corporations rarely involve themselves in politics.
E) Labor unions and corporations do not support political candidates.