Change the following sentence into passive voice. 

Raghu has purchased a new car for his brother. 

When the verb's subject (in the sentence) receives the action named in the verb, the verb is said to be in the passive voice. According to the rule on changing active voice into passive, if a sentence is in the present perfect tense (whose helping verb is "has") to convert into passive, the given sentence changes into helping verb ("has/have" to has/have + been). Therefore, option B is correct.