Identify the responsibility of the consumer ignored in the given case.

The correct option is Must obtain Cash Memo.

In consumer protection, a consumer has several key responsibilities to ensure their rights can be legally enforced. Among these, obtaining a cash memo (receipt) is one of the most critical responsibilities. A cash memo serves as legal proof of purchase, which is mandatory when lodging a complaint or claiming compensation in a consumer court for defective goods or deficient services.

Without a cash memo, a consumer cannot prove that the transaction took place with the seller in question, effectively preventing them from seeking legal remedies. Therefore, ignoring the responsibility to obtain a cash memo deprives the consumer of the right to seek redressal against unfair trade practices.