20
A)Report their illnesses.
B)Offer blood samples.
C)Act as research assistants.
D)Help to interview patients.
21
A)Strengthening people's immunity to infection.
B)Better understanding patients' immune system.
C)Helping improve old people's health conditions.
D)Further reducing old patients' medical expenses.
22Questions 22 to 25 are based on the passage you have just heard
A. .A)His students had trouble getting on with each other.
B)A lot of kids stayed at school to do their homework.
C)His students were struggling to follow his lessons.
D)A group of kids were playing chess after school.
23
A)Visit a chess team in Nashville.
B)Join the school's chess team.
C)Participate in a national chess competition.
D)Receive training for a chess competition.
24
A)Most of them come from low-income families.
B)Many have become national chess champions.
C) A couple of them have got involved in crimes.
D)Many became chess coaches after graduation.
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