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. 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. 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.
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 watch to see if it gets worse. 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.