?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.
What is the relationship between 'Syriza' and 'Alexis Tsipras' in the context of the input sentence.
Options: subsidiary, owner of, chief executive officer, chairperson