在静息情况下，细胞膜对下列哪种离子的通透性最大A．K+ B．Na+_爱下问搜题

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问题单项选择题

在静息情况下，细胞膜对下列哪种离子的通透性最大

A．K⁺

B．Na⁺

C．Cl^-

D．Ca²⁺

E．Mg²⁺

答案

参考答案：A

解析：
静息情况下，细胞膜对K⁺的通透性最大，因此K⁺可顺浓度差由细胞内向膜外扩散。

解答题

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填空题

Part 1

·Read the article below and choose the best sentence from the list on the next page to fill each of the gaps.
·For each gap (1-8) mark one letter (A-H) on the Answer Sheet.
·Do not mark any letter twice.

Noise

Do you think there is too much noise in our city If you live near the airport, you’ll be unhappy only because a jet plane flying in the sky makes loud noise. The sound of planes or heavy vehicles is likely to cause deafness if heard continuously.
(1) They like to enjoy music when they are doing dull jobs. It is a new danger because "pop" music, when played through powerful amplifiers, can reach 120 decibels at a distance of 5 feet. (2) Recently it was discovered that many teenagers hear no better than people as old as 65. (3) For example, when newspapers and books are being printed, the noise level is about 85 decibels, and some of the workers will eventually become deaf. Scientists believe that 10 percent of all workers in Britain are being deafened by the noise in the factories.
(4) We all know that too much noise makes life difficult and unpleasant. (5) Workers in noisy offices are not as efficient as those in quiet offices. Noise makes people less efficient. (6)
In Britain the government has recently made several laws to reduce noise. (7) However, many people think that there are still not enough laws. For example, there are no laws to control noise by machines. In Japan, America and Norway there are such laws. (8)
Scientists in our country are trying their best to find out one way or another to keep down noise.

A. Moreover, noise of less than 85 decibels can make some people tired and anxious.
B. However, most people in our city do not seem to mind noise.
C. Moreover, the government has spent a good deal of money in making airports and main roads quieter.
D. It can damage health and prevent people from working well.
E. Can anything be done to reduce or control noise
F. It is known that a continuous noise of over 85 decibels can cause deafness.
G. We used to think that only those who work in very noisy places became deaf.
H. As a result, workers can claim compensation if they become dea