Answer: The correct answer is "letter of recommendation".
Explanation:
The letter of recommendation effect happens when an informant gives information about a person they previously know and like. The rating the informants will give to that person in regards to personality, interpersonal qualities and so on will probably be biased towards positivity.
In this particular case, the fact that the informants are individuals who like the person they are rating they are prone to experience the letter of recommendation effect because they are motivated to depict them in a socially desirable way.