In condition (c), a person is most likely to fall sick.
The reasons are:
(a) Due to malaria, the body becomes weak and loss of body fluids occur. In this condition, it she takes four days fast, her recovery from malaria related weakness will not occur and she will become more weak.
(b) Her immune system is already weak due to malaria and if she takes care of someone suffering from chicken pox, there is high probability that she may also suffer this diseases.