A、To give an example of a bad reaction to penicillin. B、To show how penicillin has changed over the years. C、To emphasize the im

W: Hi, Dan, [23]you know which lab you missed? You can have my notes.
    M: Thanks. I appreciate that.
    W: So how are you feeling?
    M: Much better now that I began taking an antibiotic.  Students Health gave me one, and it’s really helpful.  You know what amazes me? [24] The human races survive before antibiotics.
    W: [24] I agree. When my father was a young boy in the 1940’s, he got blood poisoning and would have died. But his doctor had heard of this new drug called penicillin.
    M: Wow, he was really lucky.  And we have lots of antibiotics that kill bacteria.
    W: Well, penicillin kills bacteria, but not all antibiotics do.  Some are just slowing the bacteria down until our normal immune defense can finish the job. Tetracycline(四环素) works in that way.
    M: Wow, how do you know all these?
    W: My mother used to look up all our medicines.  There are lots of books around. It’s interesting. What antibiotic are you taking?
    M: I don’t remember. It’s on the bottle. [25] I think I’ll take a new look at the label and drop by the library to see if they have reference books on medicines. See you in the lab tomorrow.