Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: director/manager, owner of, chairperson, employer

Left-wing Syriza party leader Alexis Tsipras speaks to his supporters at Syriza's partyâ€™s main electoral center in Athens, Sunday, Sept. 20, 2015.
chairperson