Read the Following Scenario to Answer the Following Question(s)

Read the following scenario to answer the following question(s) .
Avian influenza is a viral infection that naturally occurs in wild birds with few damaging effects. However, avian influenza is highly contagious and can quickly kill domesticated birds. Some human influenza viruses are similar to the avian influenza. People infected with avian influenza develop typical flu symptoms (fever, cough, muscle aches) . However, symptoms may become more severe and life-threatening. If avian influenza evolves into a form that is easily transmissible from person to person, a global pandemic of widespread human death might occur.
-Which of the following cells would be active during an immune response to a viral infection?

A) natural killer cells
B) phagocytic cells
C) T cells
D) all of the above