In the following question, a sentence has been given in Active/Passive voice. Out of the four alternatives suggested, select the one which best expresses the same sentence in Passive/Active voice. Ram was singing a beautiful song for his mother.

• A beautiful song was being sung by Ram for his mother.
• A beautiful song was sang by Ram for his mother.
• A beautiful song was sung by Ram for his mother.
• A beautiful song was sung for his mother by Ram.