Answer: Option(a) is correct option
Step-by-step explanation:
Letter of recommendation is the letter that contain reference about a candidate for a company in the form of reference .This letter is said to have limited value because it mostly describes good traits and positive feature of candidate.Any negative direction-ed feature is not mentioned. This make every letter of almost same value.
Other options are incorrect because candidate selection for contacting reference,legal reasons and all reasons are not correct for certain value of letter of recommendation. Thus, the correct option is option(a)