问题 单项选择题 A1型题

关于促长剂的特点,不正确的是()

A.促长剂单独染毒无致癌性,必须在启动之后才发挥作用

B.大多数促长剂不需代谢活化,不与DNA共价结合

C.有可检测的阈剂量

D.通常是致突变物

E.促长作用在早期是可逆的,需要重复染毒

答案

参考答案:D

解析:促长剂可以增强引发剂的作用,其与引发剂不同在于,其作用在早期是可逆的,不需体内的代谢活化过程,有各自作用的阈剂量,与引发剂作用的先后次序十分重要,引发必须发生在促长之前,但通常不属于致突变物。

填空题
阅读理解

In the past, the affairs happening inside one country had little influence on other countries, even the neighboring ones. Therefore, incidents of food safety only affected and spread within one country, one city, one island or one village. However, with globalization, goods and products can almost flow freely between countries, regions, and continents. So the food safety problem is therefore no longer a national or regional issue, but rather a global one.

In 1997, Avian Influenza caused widespread panic in Hong Kong.It is said that the Avian Influenza originated from Shenzhen. Some Hong Kong people blamed the chicken farm staff on the mainland for the outbreak. The staff was accused of not thoroughly checking the health condition of the chicks under their care. It resulted in Hong Kong people's anger towards chicken farm staff in Shenzhen, whose supposed negligence(疏忽)contributed to the later spread of Avian Influenza in Hong Kong.

Worse still, in Germany, people have been warned not to eat cucumbers until tests can identify the source of a deadly E. coli outbreak. The scare has spread across Europe, with 16 people so far having been killed.In many people's minds, European countries have the strictest standards and checking procedures on their food safety. But the E. coli cucumber incident brought home the reality that it was not an effective defense against such an outbreak.

These diverse food safety issues from various parts of the world are enough evidence that food safety problem is not endemic in China. In fact, food safety is not even directly related to the development level of a place, thanks, no doubt, to the connectivity of our age. If we do not maintain our vigilance(警惕), people's confidence in food safety can be destroyed instantly—even in a developed country

小题1:Which of the following is true according to the passage?

A.Nowadays, food safety incidents spread inside one country

B.In 1997, Avian Influenza caused great fear in Hong Kong

C.16 Germans died of deadly E. coli after eating cucumbers

D.Food safety is only related to the developing countries小题2:The underlined word "endemic" in the last paragraph most probably means "______"

A.serious

B.common

C.urgent

D.unique小题3:We can infer from the passage that ______

A.food safety problems spread from one country to another

B.the staff of a Shenzhen chicken farm caught Avian Influenza

C.the strictest standards protected European people from getting E. coli

D.China is a country where food safety problem is related to people's age小题4:Which of the following would be the best title for the passage?

A.Food Safety Problem Is a Global Issue

B.Cucumbers Are Popular in European Countries

C.Avian Influenza Originated from Shenzhen

D.Food Safety Issues Are Various from Country to Country