The correct answer is D. The beggar was laughed at by the boy.
The sentence “The boy laughed at the beggar” is in the active voice. This means that the subject of the sentence, “the boy,” is performing the action of the verb, “laughed.” The direct object of the sentence, “the beggar,” is receiving the action of the verb.
In the passive voice, the subject of the sentence receives the action of the verb. The direct object of the sentence becomes the subject of the sentence. In the sentence “The beggar was laughed at by the boy,” the subject is “the beggar” and the direct object is “the boy.” The verb is “laughed at.”
The sentence “The beggar was being laughed at by the boy” is in the progressive passive voice. This means that the action of the verb is happening over time. The sentence “The beggar was laughed at by the boy” is in the simple passive voice. This means that the action of the verb happened once.
The sentence “The beggar was laughed by the boy” is grammatically incorrect. The verb “laugh” does not take a direct object.