This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
To control pain in long standing cancer cases, the recommended route of administration is: 
Select and explain. 
A. i.v, B. Subcutaneous, C. Sublingual, D. Oral
D: Oral
Answer: D: Oral 
Explanation: Oral route is the preferred route for administration of analgesics in cancer patients, even for long standing pain due to ease of dosing, reliability and convenience.