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: Pathology
Which of the following oncogenes is a growth factor? 
Select and explain. 
A. fos, B. myc, C. jun, D. sis
D: sis
Answer: D: sis 
Explanation: The 'sis' oncogene is a growth factor. The protooncogene 'sis' encodes the ( b chain of) Platelet Derived Growth Factor (PDGF). Ref: Robbin's Illustrated Pathology, 7th Edition, Pages 293, 295; Cancer: Principles and Practice of Oncology, 6th Edition, Page 13