What is the relationship between Williams Companies and natural gas 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.

Within this article: Details on U.S. natural gas pipeline projects, including those from major companies such as Kinder Morgan Incorporated ( KMI ), TransCanada Corporation ( TRP ), Spectra Energy Corporation ( SE ) and Williams Companies ( WMB ).

Answer: product_or_material_produced