Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: distributed by, industry, owner of, chairperson

Greek PM Tsipras under pressure over covert Syriza drachma plan reports 34 minutes ago Greek Prime Minister Alexis Tsipras in Athens, Greece July 24, 2015.
chairperson