Minor changes of HA are called A: Gene mutation B: Gene reassortment C: Antigenic shift D: Antigenic drift

Immune defense means that the body can () A: resist to invasion of pathogens and neutralize their toxic products B: exclude the aging and injuried cells and keep the balance of inner<br/>environment C: surveil and clear transformed cells inside the body D: present unresponsive state to antigenic foreign substances E: present unresponsive state to self antigenic