Correct Answer: (b) Guinea, Sierra Leone and Liberia
Solution:The first two cases of Ebola virus were reported in Sudan and the Democratic Republic of Congo in 1976, followed by the March, 2014 case of Ebola virus in West Africa. Guinea, Sierra Leone and Liberia were the worst affected. Liberia, Sierra Leone and Guinea were declared Ebola-Free by the 'World Health Organization' (WHO) in October, November and December 2015 respectively.