Final answer:
A broker must retain each brokerage transaction record for 3 years according to section 371.2 of the FMCSA DOT Laws and Requirements.
Step-by-step explanation:
According to section 371.2 of the FMCSA Department of Transportation Laws and Requirements, a broker must keep a record of each brokerage transaction for a period of 3 years. This requirement ensures that records are available for audit and compliance review by the FMCSA or other authorized agencies. The rationale behind this regulation is to maintain a transparent record-keeping system that can be used to verify the legality and efficiency of brokerage operations.