What is the main purpose of recording the lot number, wafer number and on-wafer coordinates during wafer test in electrically programmable non-volatile memory (such as fuses) inside an automotive IC?

Answer: C. To identify the lot, wafer and position of a returned failed chip and cross-reference it with manufacturing and test records

Once a chip is sealed in a package, you cannot tell from outside which wafer it came from or where on the wafer it was. If identification data is written into the chip, it can be read out when a failed part is returned from the field, tracing back to manufacturing conditions and even wafer test measurements. It also helps narrow down which other products processed on the same equipment might be affected. This is chip-level traceability. Encryption keys generally use a separate dedicated mechanism that is hard to read out.