What is the relationship between Frozen and single in the context of the input sentence. Choose an answer from: 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.

For the fourth quarter, total Conagra Frozen retail sales grew 26.2% over last year with strong growth across each Frozen category, including single serve meals, vegetables, multi-serve meals, and plant-based meat alternatives.

Answer: distribution_format