To evaluate the provided options and identify which deal is not a large, billion-dollar transaction entered into by IT majors in India, we must cross-reference each option against documented significant deals in the IT industry:
- TCS-Nielson: Tata Consultancy Services (TCS) has indeed engaged in significant deals, but there is no notable documentation or announcement of a multi-billion dollar deal specifically with Nielson.
- Tech Mahindra-BT: Tech Mahindra has been involved in massive agreements with BT Group, notably taking over substantial parts of BT's staff and infrastructure in past transactions.
- Infosys-BN AM O: Infosys has participated in various substantial deals, but there is inadequate or nonexistent information on a major billion-dollar agreement with BN AM O, suggesting this option is not a billion-dollar deal.
- IBM-Bharti: IBM has a history of securing large deals with Bharti Airtel, including strategic IT partnerships valued in billions.
Based on the verification process, the information suggests that Infosys-BN AM O is the option that stands out as not being a billion-dollar deal.