Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: chief executive officer, chairperson, subsidiary, owner of

?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