A patient after undergoing thoracotomy complains of severe pain. He can be managed by –
Gold standard for management of post-thoracotomy pain → Epidural opioids (epidural analgesia)
But, amongst the given options IV fentanyl (IV opioid) is the best answer.

Management of post-thoracotomy pain

Gold Standard → Central neuraxial analgeria (Thoracic epidural opioids)
Second choice → Parentral opioid
Intercostal cryoanalgesia
I.V. fentanyl
Oral morphine
Oral brufen