Concept:Data retrieval methods differ in speed based on how the file is searched for a record.
Explanation:Sequential access reads records one after another from the start of the file.
To find a required record, every record before it must also be read.
If the target record is near the end, this consumes much more time.
Direct access allows jumping straight to a known storage location.
Indexed access uses an index to locate the record quickly without scanning the whole file.
Random access also enables immediate retrieval of any record without prior records.
Compared with these methods, sequential access is slower and less efficient because it depends on the position of the data.
It is least efficient when the needed data is far from the beginning of the file.
Answer:Sequential access is the least efficient method for data retrieval.