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

The latest news from Greece, where Prime Minister Alexis Tsipras contained a rebellion in his left-wing Syriza party to win a parliamentary vote, was seen as another positive for European markets.
chairperson