A、It was a serum prepared from the blood of patients who had been stung. B、It was a serum prepared from poison extracted from be

A team of researchers has found that immunizing patients with bee venom instead of with the bees’ crushed bodies can better prevent serious and sometimes fatal sting reactions in the more than one million Americans who are hypersensitive to bee stings. The crushed-body treatment has been ineffective. The serum made from the crushed bodies of bees produced more adverse reactions than the injections of the venom did.
    The research compared results of the crushed-body treatment with results of immunotherapy that used insect venom and also with results of a placebo. After six to ten weeks of immunization, allergic reactions to stings occurred in seven of twelve patients treated with the placebo, seven of twelve treated with crushed-body extract, and one of eighteen treated with the venom.
Questions 26 - 30 are based on the passage you have just heard.
26. What is the main topic of the passage?
27. What can we learn about the traditional treatment for bee sting according to the researchers?
28. What was the most successful treatment described in the passage?
29. How should the treatment referred to in the passage be administered?
30. What did the results of the experiment indicate?