判断水质是否受人畜粪便污染的最重要指标是（）
A.细菌总数
B.大肠菌群
C.粪大肠菌群
D.肠道致病菌
E.厌氧芽孢菌
参考答案：C
解析：总大肠菌群是指一群需氧及兼性厌氧的在37℃生长时能使乳糖发酵、在24小时内产酸产气的革兰阴性无芽孢杆菌。人体肠道内存在大量的大肠菌群细菌，其他温血动物，如牛、羊、狗等的肠道内也存在大量的大肠菌群细菌，在土壤、水等自然环境中也可存在大肠菌群细菌。由于人粪便中存在大量的大肠菌群细菌，因此这种细菌可作为粪便污染水体的指示菌。来自人及温血动物粪便内的大肠菌群主要属粪大肠菌群，因此如果要准确判断是否受到人畜粪便污染要利用提高培养温度的方法来区别不同来源地大肠菌群细菌，及培养于（44．5±0．2）℃的温水浴内能生长繁殖使乳糖发酵而产酸产气的大肠菌群细菌，称为粪大肠菌群。因而选择C。
Passage One
| With the possible exception of equal rights, perhaps the most controversial issue across the United States today is the death penalty. Many argue that it is an effective deterrent (威慑) to murder, while others maintain there is no convincing evidence that the death penalty reduces the number of murders. The principal argument advanced by those opposed to the death penalty, basically, is that it is cruel and inhuman punishment, that it is the mark of a brutal society, and finally that it is of questionable effectiveness as a deterrent to crime anyway. In our opinion, the death penalty is a necessary evil. Throughout recorded history there have always been those extreme individuals in every society who were capable of terribly violent crimes such as murder. But some are more extreme than others. For example, it is one thing to take the life of another in a fit of blind rage, but quite another to coldly plot and carry out the murder of one or more people in the style of a butcher. Thus, murder, like all other crimes, is a matter of relative degree. While it could be argued with some conviction that the criminal in the first instance should be merely isolated from society, such should not be the fate of the latter type murderer. The value of the death penalty as a deterrent to crime may be open to debate. But the overwhelming majority of citizens believe that the death penalty protects them. Their belief is reinforced by evidence which shows that the death penalty deters murder. For example, from 1954 to 1963, when the death penalty was consistently imposed in California, the murder rate remained between three and four murders for each 100 000 population. Since 1964 the death penalty has been imposed only once, and the murder rate has risen to 10.4 murders for each 100 000 population. The sharp climb in the state’s murder rate, which began when executions stopped, is no coincidence (巧合). It is convincing evidence that the death penalty does deter many murderers. If the bill reestablishing the death penalty is vetoed (否决), innocent people will be murdered—some whose lives may have been saved if the death penalty were in effect. This is literally a life or death matter. The lives of thousands of innocent people must be protected. |
It can be inferred that the author thinks that ______ .
A．the veto of the bill reestablishing the death penalty is of little importance
B．the value of the death penalty as a deterrent to crime is not to be debated
C．the death penalty is the most controversial issue in the United States today
D．the second type murderers (in Para. 4) should be sentenced to death