Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: employer, chairperson, industry, headquarters location

ATHENS (Reuters) - The leftist Syriza party of former Prime Minister Alexis Tsipras will challenge Greece's creditors on unresolved aspects of the nation's bailout but implement unpopular reforms it has already agreed, it said on Sunday.
chairperson