Answer: They are classified by subtypes based on the properties of their hemagglutinin (H) and neuraminidase (N) surface proteins. There are 18 different HA subtypes and 11 different NA subtypes. Subtypes are named by combining the H and N numbers.
1.There movement: People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.
2. There protein structure: The influenza viruses are classified into types A, B, and C on the basis of their core proteins. Type A viruses are further subdivided according to their envelope glycoproteins with haemagglutinin (HA) or neuraminidase (NA) activity.
3. There genetic material: by subtypes based on the properties of their hemagglutinin (H) and neuraminidase (N) surface proteins. There are 18 different HA subtypes and 11 different NA subtypes. Subtypes are named by combining the H and N numbers – e.g., A(H1N1), A(H3N2)
4. Different shapes: I don't know that one
Explanation: Hope this helps though :)