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
Transitional cell carcinomas can be caused by -a)  Napthylamineb)  Smokingc)  Bilharziasisd)  Betel nut 
Select and explain. 
A. abc, B. bc, C. acd, D. bcd
A: abc
Answer: A: abc 
Explanation: None