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: Microbiology
Viruses causing hemorrhagic fever are-a) Lassa fever virusb) Yellow fever virusc) West Nile virusd) Crimean Congo viruse) Ross river virus 
Select and explain. 
A. abd, B. bcd, C. abc, D. ab
A: abd
Answer: A: abd 
Explanation: None