单选题 {{B}}TEXT 3{{/B}}

When a disease of epidemic proportions rips into the populace, scientists immediately get to work, trying to locate the source of the affliction and find ways to combat it. Oftentimes, success is achieved, as medical science is able to isolate the parasite, germ or cell that causes the problem and finds ways to effectively kill or contain it. In the most serious of cases, in which the entire population of a region or country may be at grave risk, it is deemed necessary to protect the entire population through vaccination, so as to safeguard lives and ensure that the disease will not spread.
The process of vaccination allows the patient's body to develop immunity to the virus or disease so that, if it is encountered, one can ward it off naturally. To accomplish this, a small weak or dead strain of the disease is actually injected into the patient in a controlled environment, so that his body's immune system can learn to fight the invader properly. Information on how to penetrate the disease's defenses is transmitted to all elements of the patient's immune system in a process that occurs naturally, in winch genetic information is passed from cell to cell. This makes sure that, should the patient later come into contact with the real problem, his body is well equipped and trained to deal with it, having already done so before.
There are dangers inherent in the process, however. On occasion, even the weakened version of the disease contained in the vaccine proves too much for the body to handle, resulting in the immune system succumbing, and, therefore, the patient's death. Such is the case of the smallpox vaccine, designed to eradicate the smallpox epidemic that nearly wiped out the entire Native American population and killed massive numbers of settlers. Approximately 1 in 10,000 people who receives the vaccine contract the smallpox disease from the vaccine itself and dies from it. Thus, if the entire population of the United States were to receive the Smallpox Vaccine today, 3,000 Americans would be left dead.
Fortunately, the smallpox virus was considered eradicated in the early 1970's, ending the mandatory vaccination of all babies in America. In the event of a re-introduction of the disease, however, mandatory vaccinations may resume, resulting in more unexpected deaths from vaccination. The process, winch is truly a mixed blessing, may indeed hide some hidden curses.

单选题 The best title for the text may be ______.

单选题 What does the example of the Smallpox Vaccine illustrate?

【正确答案】 A

【答案解析】[解析] 题目问：“天花疫苗这个举例是说明什么情况?”此题可定位于第3自然段，且第3、4自然段的主题就是使用疫苗可能会带来负面效果，因此选项[A]“使用疫苗可能会带来负面结果”为正确选项。而选项[B]“疫苗的实际使用来控制传染病”，选项[C]“疫苗在于消除某些疾病的有效性”和选项[D]“疫苗对付疾病所使用的方法”都不是这个举证所谈论的观点。

单选题 The phrase "ward it off naturally" (Paragraph 2) most probably means ______.

单选题 Which of the following is true according to the text?

【正确答案】 B

【答案解析】[解析] 题目问：“根据这篇文章，下面哪项是对的?”纵观全文，本文的中心讲的是免疫系统可以得到特殊的训练以应对疾病的较弱形式，因此选项[B]“免疫系统可以得到特殊的训练以应对疾病的较弱形式”为正确选项。而选项[A]“挽救大多数的人必然造成少数人的死亡”，选项[C]“强制性的接种对于大众的生存是不可或缺的”和选项[D]“接种的过程仍然是一个应该解决的神秘”都不能说明原文的含义。