The regulator further said that only Bharti Airtel in Mumbai and Tata Teleservices in Delhi met the laid-down quality of service (QoS) benchmarks for call drop rate, which as per norms should be less than 2%.
Take context from the input text and decide on the accurate relationship between 'Tata Teleservices' and 'Mumbai' from the options provided.
Options: owner of, headquarters location, business division, developer