Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: chief executive officer, owner of, subsidiary, chairperson

?Equity markets largely in the red... coming down off yesterday's heady reaction to news of a Greek deal, as Alexis Tsipras returns to a revolution within his Syriza party," said Augustin Eden, research analyst at trading firm Accendo Markets.
chairperson