Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: owner of, distributed by, chairperson, industry

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