<prompt> A patient is having a malignancy and has been suffering from severe pain. Which of the following opioid analgesics can be used as transdermal patch for alletion of pain in him?MorphinePentazocineFentanylTramadol  <response>: Ref: KDT 6e p459 Fentanyl can be used as a transdermal patch for prolonged treatment of cancer associated pain. 