Utilize the input text as a context reference, choose the right relationship between eurozone and euro from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Greece's fellow eurozone members have widely rounded on Mr Tsipras for backing a 'No' vote, warning that he must choose between keeping the euro or returning to the drachma.

Answer: currency