Already, Prime Minister Alexis Tsipras is struggling to contain a rebellion in his leftwing Syriza party that made his government dependent on votes from pro-European opposition parties to get the tough bailout terms approved in parliament.
Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: distributed by, product/material produced, chief executive officer, chairperson