Which of the following can be used safely in a carcinoma patient with intractable pain:
a. Opioids by any route are excellent choice for cancer patients.
b. Oral route is preferred over parenteral route because of compliance but is reserved only for mild to moderate cases.
c. Severe intractable pain requires parenteral therapy.
d. Ketamine is an excellent analgesic but is not used for providing analgesia because of its side effects like hallucinations, vivid dreaming and delirium.