-Anitha Dunga : Subject Matter Expert at Edumarz
Answer : In condition (c) the person is most likely to fall sick
In (c) there are maximum possibilities for a person to fell ill, because when the person is on the fourth day of the recovery from malarial means she is not completely recovered, immune system of her is still weekend and in that time when she is exposed to the person who is suffering from the chicken pox, there are maximum possibilities for her to get infected with the chickenpox virus. Also infection at this time causes severity in disease because the immune system gets weakened by malaria parasites.
In condition (a) the person is recovering from the malaria and she has not come in contact with any other, so the possibility of falling sick was less.
In condition (b) she has come in contact with the person who is suffering with chicken pox after she has recovered from the malaria infection. So that recovery from infection makes the immune system stable and helps in preventing new infections.