[问答题]
The question is based on z;0 ag )s5wvxxchk js p7:c m0 3 8es7ts4h.evnq2/vyathe second passage you have just heard.
参考答案: The function of the human immune system.
The cause of various auto-immune diseases.
The viruses that may infect the human immune system.
The change in people's immune system as they get older.
