What is the relationship between grocery and Walmart 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.

"We continue to believe that Walmart must generate low-single-digit comp-store sales growth in its U.S. grocery business to drive sustainable positive traffic and low-single-digit consolidated comp-store sales," he said.

Answer: operator