Correct option is B
"A letter was being written by Rahim" is the correct passive voice transformation of the given sentence. It changes the active voice sentence into passive voice while maintaining the correct tense and structure.
· Active Voice- Active voice is a grammatical structure in which the subject of the sentence performs the action expressed by the verb.
· Passive Voice- Passive voice refers to a grammatical construction where the subject of a sentence undergoes an action rather than performing it. In passive voice sentences, the emphasis is on the recipient or object of the action.
Conversion rule: Subject + was, were + verb + ing + object -> <- Object + auxiliary verb (was, were) + being + past participle + by + subject.