The correct response based on the investigation of Russian imperial methods of political control is:
"The tsar was head of the empire and the most powerful, but he had to work with others to achieve political control."
This option accurately reflects the reality of the tsar's position within the Russian Empire, where while the tsar held ultimate authority, he often relied on various institutions, advisors, and other leaders to maintain and exercise political control effectively. Additionally, the other statements either oversimplify or misrepresent the complexity of political relations and control during the Russian Empire.