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: Pharmacology
Which of the following anti-HIV drug should never be given as re–challenge once history of producing allergic reaction with drug is known ? 
Select and explain. 
A. Lamivudine, B. Abacavir, C. Zidovudine, D. Nelfinavir
B: Abacavir
Answer: B: Abacavir 
Explanation: None