问题 单项选择题

心室肌细胞动作电位平台期是下列哪些离子跨膜流动的综合结果

A.Na+内流,Cl-外流

B.Na+内流,K+外流

C.Na+内流,Cl-内流

D.Ca2+内流,K+外流

E.K+内流,Ca2+外流

答案

参考答案:D

解析:题解:此期膜电位下降极缓慢,停滞于接近零的等电位状态,形成平台状。是Ca2+内流,K+外流引起。2期平台是心室肌细胞动作电位的主要特征,是与神经纤维及骨骼肌动作电位的主要区别。

选择题
阅读理解

On April 24th, another natural disaster—the oil spill(泄露) in the Gulf of Mexico, happened.Millions of dollars have been used to help stop the spill and to clean up the animals, beaches, and land spoiled by the oil.Unfortunately, when many of these chemicals are used, more damage is caused to the environment, especially to lives in the sea.

But governments seem to accept the risk of transporting millions of tons of oil by ship every day so that we can fill up our cars and drive around and cause even more environmental damage.Interestingly, the biggest companies in the world produce cars, and the next biggest supply the gasoline to make them run.

Of all of today's environmental disasters, an oil spill may actually be one of the least serious.Although oil is poisonous, it is a natural material.In the end, it breaks down naturally.In 1967 the tanker Torrey Canyon sank off the Scilly Isles near the coast of England and spilled 120,000 tons of oil into the ocean.If you go there today, you will find it hard to see any sign that it ever happened.      

However, we should be thinking more about reducing our dependency on oil.Governments should be encouraging research into new technologies, such as cars run by solar power(太阳能), electricity, hydrogen, and so on.Much of this research, in the past, was stopped by the oil, gas, and coal.

If the world's millions of cars were 10% more efficient(高效的),we would need many fewer tankers crossing the oceans each year.If this happened, the risks of oil spills would be reduced, and the air we breathe would be cleaner and fresher, too.

小题1:What is the passage mainly talking about?

A.Oil spills pollution.

B.What oil pollution is.

C.Oil tanker accidents.

D.How to reduce oil pollution.小题2:How does the author support the idea that oil spills are not as serious as people believe?

A.By giving a description.

B.By making an argument.

C.By giving an example.

D.By comparing.小题3:Which suggestion is made for reducing oil tank accidents according to the passage?

A.We should build safer tankers in the near future.

B.We should develop new technologies to cut oil use.

C.Tankers should not be allowed to sail near the coastlines.

D.Countries should build more oil pipelines under the sea.小题4:Where can you read this article?

A.In a story book.

B.In a science magazine.

C.In a novel.

D.In a travel guide.