Correct Answer: Let the migrant workers be helped.

Solution : The fourth option is the correct answer.

Passive voice is a grammatical construction where the subject of the sentence undergoes the action expressed by the verb rather than performing it. In the active sentence, the subject is "you," or an implied subject. When converting this into the passive voice, the structure becomes "Let + object + be + past participle". In this case, the object is "the migrant workers," and "helped" is the past participle of the verb "help". The phrase "let" is used to indicate permission or a suggestion in the passive construction.

Therefore, the correct answer is: Let the migrant workers be helped.