Answer:
Option b they create genetic variations
Step-by-step explanation:
Mutation can cause genetic variations on a virus. The genetic variations can be catastrophic as the mutated virus might grow resist to certain drug and cause treatment become harder. Besides, virus also has a high mutation rate and this is a medical challenge to design an effective treatment that can work from time to time. The high mutation rate of viruses also enable them to easily adapt themselves to a host environment.