What is the relationship between Telstra and David Thodey 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.

David Thodey engineered a stunning turnaround at Telstra , extending its dominant position in the mobile sector, negotiating lucrative agreements with the government (twice) over the National Broadband Network, selling off non-core assets and cutting expenses.

Answer: chief_executive_officer