A．this sentence contributes to the increase of the number of lymphocytes in your body
B．you would not realize that lymphocytes reproduce themselves rapidly but for this sentence
C．because you read this sentence, a large number of lymphocytes have been consumed
D．the number of lymphocytes in your body is extremely large

A．Thymus
B．Transplants
C．Cancer ceils
D．Healthy cells

A．How does the immune system attack the flu virus?
B．How does the immune system function in our body?
C．How do the lymphocytes work in our body?
D．What is the so-called immune system?