问题 单项选择题

被疟原虫寄生的红血球在人体内的存在时间不会超过120天。因为疟原虫不可能从一个它所寄生的衰亡的红血球进入一个新生的红血球。因此,如果一个疟疾患者在进入了一个绝对不会再被疟蚊叮咬的地方120天后仍然周期性高烧不退,那么,这种高烧不会是由疟原虫引起的。
以下哪项,如果为真,最能削弱上述结论

A.由疟原虫引起的高烧和由感冒病毒引起的高烧有时不容易区别。

B.携带疟原虫的疟蚊和普通的蚊子很难区别。

C.引起周期性高烧的疟原虫有时会进人人的脾脏细胞,这种细胞在人体内的存在时间要长于红血球。

D.除了周期性的高烧只有到疟疾治愈后才会消失外,疟疾的其他某些症状会随着药物治疗而缓解乃至消失,但在120天内仍会再次出现。

答案

参考答案:C

解析:如果C项为真,则能说明,如果一个疟疾患者在进入了一个绝对不会再被疟蚊叮咬的地方120天后仍然周期性高烧不退,那么,这种高烧仍然可能是由进入人的脾脏细胞的疟原虫引起的,这就有力地削弱了题干的结论。
其余各项均不能削弱题干。

单项选择题 A1/A2型题
单项选择题

A

Imagine, one day, getting out of bed in Beijing and being at your office in Shanghai in only a couple of hours, and then, after a full day of work, going back home to Beijing and having dinner there.

Sounds unusual, doesn’ t it But it’ s not that unrealistic, with the development of China’ s high-speed railway system. And that’ s not all. China has an even greater high-speed railway plan to connect the country with Southeast Asia, and eventually Eastern Europe.

China is negotiating to extend its own high-speed railway network to up to 17 countries in 1 0 to 15 years, eventually reaching London and Singapore.

China has proposed three such projects. The first would possibly connect Kunming with Singapore via Vietnam and Malaysia. Another could start in Urumqi and go through Kazakhstan and Uz-bekistan, and possibly to Germany. The third would start in the northeast and go north through Russia and then into Western Europe.

If China’ s plan for the high-speed railway goes forward, people Could zip over from London to Beijing in under two days.

The new system would still follow China’ s high-speed railway standard. And the trains would be able to go 346 kilometers an hour, almost as fast as some airplanes.

China’s bullet train(高速客车), the one connecting Wuhan to Guangzhou, already has the World’ s fastest average speed, It covers 1,069 kilometers in about three hours.

Of course, there are some technical challenges to overcome. There are so many issues that need to be settled, such as safety, rail gauge (轨距), maintenance of railway tracks. So it’s important to pay attention to every detail.

But the key issue is really money. China is already spending hundreds of billions of yuan on domestic railway expansion.

China prefers that the other countries pay in natural resources rather than with capital investment. Resources from those countries could stream into China to sustain development.

It’ll be a win-win project. For other countries, the railway network will definitely create more opportunities for business, tourism and so on, not to mention the better communication among those countries.

For China, such a project would not only connect it with the rest of Asia and bring some much-needed resources, but would also help develop China’ s far west. We foresee that in the coming decades, millions of people will migrate to the western regions, where the land is empty and resources unused. With high-speed trains, people will set up factories and business centers in the west once and for all. And they’ 11 trade with Central Asian and Eastern European countries.

Which of the following might be the best title for the passage()

A. New Railway Standards

B. Big Railway Dreams

C. High-speed Bullet Trains

D. International Railway Network