A、Because he is too young to catch that. B、Because he has not been exposed to that. C、Because his sister hasn’t caught that. D、B

M: Hello, how can I help you?
W: My son isn’t feeling well and I’d like to get some advice.
M: What seems to be the problem?
W: Well, he has been coughing for several days now. (19) I’m wondering if he should come in and see the doctor.
M: How old is he?
W: He is 3 years old.
M: Does he have any other symptoms like fever, runny nose or loss of appetite?
W: No, actually other than the cough, he seems healthy. I am concerned though, because some of his sister’s friends have whooping cough and I know that it can be very contagious. (20) Isn’t that a pretty serious illness?
M: It can be serious with babies. Has your son been immunized against whooping cough?
W: I’m not sure. He did get all of the suggested vaccinations. I will look it up in our records.
M: If he has been immunized recently, it is very unlikely that he would catch whooping cough, even if he has been exposed. (21)
W: Sounds like I don’t have to worry about that, but what shall I do about his cough?
M: It will help if you give him lots of fluids and a hot bath before bedtime. Keep an eye on the cough to see if it gets worse. (22) Call us again if he has a fever or if you are still concerned.
W: Thanks for your advice.
M: You are welcome. Good-bye.
W: Bye-bye.
19. What’s wrong with the child?
20. Why is the mother worried about the child’s cough?
21. Why does the doctor think that it is unlikely for the child to catch the whooping cough?
22. Which of the following is NOT a suggestion the doctor gives the mother?