Answer:
The correct answer is - antigenic shift due to mutation.
Step-by-step explanation:
In this image, there is a representation of the antigenic shift or change takes place to evolve to a new strain of influenza virus from the original virus that has a different antigen on the surface of the virus than the new strain. In this image it is shown that the surface H antigens went through a shift to form a new strain while N antigen remain the same.
This is important to adapt and evolve according the internal environment of the host show this type of mutation requires if moving from one host to another (human to pigs).