Convert the following sentence into passive form. 

"The boys are cooking lunch for the guests."

In the active voice, the subject performs the action. The given sentence, "The boys are cooking lunch for the guests", is in the active voice format. Here, the subject of the sentence "boys" is the doers of the action "cooking". We need to convert the sentence into the passive form where the subject receives the action in the name of the verb. In the passive voice, the subject will be shown as affected by the verb. The given statement is in the present continuous tense. We have to use "being" and the past participle form of the verb("cooking" becomes "cooked") in order to make it into the passive form. Option A does not use "being", and hence it is wrong. Option C is in the past continuous tense, and option D is in the present perfect tense. Option B follows the mentioned rules, and hence, it is correct.