What is the relationship between Willis Group and insurance broker 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.

In early March, when merger talks were under way between Towers Watson TW, -0.76% and insurance broker Willis Group Holdings PLC WSH, -1.82% , Haley exercised 106,933 stock options and sold the underlying shares for a $9.7 million profit, according to regulatory filings.
industry