Which of the following records must be retained for 6 years according to SEC rules?

The requirement for retaining records for 6 years according to SEC rules is specifically applicable to certain types of records that are essential for compliance, oversight, and potential audits. Receipts of cash fall under this requirement as they are critical for financial audits and ensuring transparency in transactions. Keeping detailed records of cash receipts helps in tracking cash flows and validating the financial integrity of transactions over time.

In contrast, other options such as records of fails to deliver and order execution confirmations may have different retention periods. Daily trading logs, while important for record-keeping and regulatory oversight, also may not fall under this specific 6-year rule. Each type of record is governed by its specific regulatory guidelines, highlighting the importance of understanding these requirements for proper compliance in the securities industry.