Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: parent organization, industry, stock exchange, chairperson

ATHENS, Sept 20 The leftist Syriza party of Alexis Tsipras has won 35.54 percent of the vote in Sunday's Greek national election based on 50 percent of votes counted, the Interior Ministry said on its website.
chairperson