Select the option that expresses the given sentence in passive voice.

Alfred’s doctor treated Rohan for his fever.

Rohan was treated by Alfred’s doctor for his fever.

The correct passive voice of the given sentence is Rohan was treated by Alfred’s doctor for his fever.

The active voice of the sentence is Alfred’s doctor treated Rohan for his fever. This sentence is in the simple past tense, which is used to describe an action that happened in the past. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "Rohan" and the main verb is "treat." The past participle of "treat" is "treated." So, the passive form of the sentence is Rohan was treated by Alfred’s doctor for his fever.

The other options are incorrect because:

• Rohan will be treated by Alfred’s doctor for his fever. is in the future tense, while the original sentence is in the simple past tense.
• Rohan has been treated by Alfred’s doctor for his fever. is in the present perfect tense, which is used to describe an action that has happened in the past but is still relevant to the present. The action of treating Rohan for his fever is not something that is still relevant to the present.
• Rohan was treats by Alfred’s doctor for his fever. is grammatically incorrect. The verb "was" is singular. The subject of the sentence is "Rohan," which is plural.